I have never used an OM-1 but in the Canon R body world that can still use your present lenses the RP is the smallest, lightest full frame. Smaller than the OM-1.
I have an RP and R7 that between them cover just about everything I photograph. With two EF to RF adapters I also can use all my EF and EF-s lenses (I still have 2 full frame and 3 crop sensor EF bodies). And in the R body world all the RF and RF-s lenses will fit on and work with all the R bodies. Put an RF-s lenses on a full frame R body and it automatically goes into crop sensor mode. The RP in crop mode does 10MP images.

Here is more or less complete comparison: https://cameradecision.com/compare/OM-System-OM-1-vs-Canon-EOS-RP

I shot with (mostly) Nikons from 1970 'til 2017, and Leica rangefinders, Hasselblad, Rolleiflex, Mamiya TLR, Ricoh, Olympus and others I've forgotten alongside. Switched from film to Nikon digital in 2004 and took -0- film images after that. My normal Nikon kit included the trilogy of f/2.8 zooms covering 17-200mm, but I had many other zooms and primes available over the years, mostly FF from the film days. My last Nikon bodies were a D7000 (DX) and a D600 (FX).

On a whim I bought a used Lumix GX85 at the local camera store in 2017 because a friend (with WAY more photo equipment - including a 48 inch photo printer) had one and raved about it. I loved the smaller size and lower weight, and even with the tiny 12-32 collapsible kit lens I found the MFT image quality to be more than good enough for my purposes. I pretty promptly switched to MFT equipment, and sold my Nikon gear in 2018.

I've gone through the Olympus OM-D EM1 bodies, and have settled on the MkIII with a MkII for backup. (I tried the Lumix G9, which is a lovely machine, but I get MUCH better/faster autofocus on my young speedy grandchildren in low light with the Olympus bodies so I let the G9 go.) I have a collection of Olympus and Lumix prime and zoom lenses from 9-18mm through a 45-150mm kit zoom, and except for the Oly 12-40 and PanaLeica 12-60 f/2.8 zooms they're all smaller and lighter than any Nikon lens I had. A typical kit for me now is the MkIII body with the 12-40 or 12-60 zoom lens, plus the 9-18 zoom and an Olympus flash. If I think I might want the 45/1.7 I have a coupler to stack it with the 9-18 and still have a lens package smaller and lighter than the "big" zoom on the camera. All in a bag less than half the size and way less than half the weight of what I used with the Nikons. For a quick shot around the house, like an owl on a fence post or a deer in the front yard, the MkIII with a Lumix 12-60 kit zoom (my favorite walkin' around package) sits on a counter ready to grab.

I have NEVER had the thought when processing a file in Lightroom "gee, if I'd used my full frame Nikon gear I could make a better print of this." My needs are simple, though - I make 8x8 B&W prints with Canon Pro 10 printers, that get bound into books for family members. No posters, and no blowups of tiny sections of an image. If there's a difference in depth of focus at f/2.8 between the MFT and my old FF images I don't notice and so don't care. As I said, the image quality from the 20MP sensor is more than good enough for what I print.

What I DO think of fairly regularly, although only in passing, is how small and light my kit is. One of my most vivid memories of a Nikon shoot was the weekend I rented a 300/2.8 to use at a horse show (in the film days, probably with an F100, my favorite Nikon film body) and how much my shoulder still hurt on Monday when I took the thing back to the camera store to turn in. (I snarled at 'em asking why they didn't give me the wheel set for it, because even attached to a monopod carried over my shoulder it was a BEAST to move around.) Then last year I rented the Olympus 40-150/2.8 (80-300 FF equivalent) to use at another horse show and thinking what a delight it was to have a package that fast, small and light WITH a wide zoom range to boot, compared to the howitzer of a Nikon I had carried around years earlier. I don't do enough horse shows now to justify owning that particular Olympus lens, but if my needs change (it's up to my daughter, who rode in LOTS of shows when we paid for it, but since she got married . . . ) I will be happy to add that lens to my MFT arsenal. Although, to be honest, I switched back and forth with a Lumix 45-150 kit zoom over the 2-day show, and the kit lens did an awfully good job too.

So overall, if weight is an issue, by all means take a good look at MFT as an alternative for your FF gear. If you have especially demanding requirements (be honest about it - we all want "the best quality possible", but if you have to pixel-peep to see the difference, and can only see it in a split screen, side by side comparison, do you reeeeeeally need it?) you probably should consider renting an outfit that approximates what you currently use. And set up a careful side by side test to see if the ACTUAL OUTPUT (not pixel peeping) from the new gear will do what you need.

FWIW, I used top-range FF Nikon DSLR’s since they appeared. Worked well for my purposes. Last one was the D810 — their best model at the time. I was on the waiting list for the upgrade to the forthcoming D850. But, I’d become increasing tired of Nikon’s standard cycle of bigger, more expensive ‘but improved cameras’, and ditto with the lenses. The issue wasn’t that they were too big/heavy for me to carry. I was just annoyed, and also felt that the gear was becoming simply too intrusive, and I just was not ‘enjoying’ photography as much, although they were terrific cameras/lenses, and I’d been selling some images in a small gallery and on line. So I started looking around. My past experiences of traveling with a small Leica influenced my thinking. So, I began looking at mirrorless. Checked out the Sony FF at the time. But, their FF sensor size drove up the sizes of their lenses. Looked at the Fuji’s. (Nikon mirrorless was not yet in the market; but, looking at them since moving to Oly, I feel no urge to change back.) Then, looked closely at the Olympus M1Mk2 (later upgraded to the current OM-1). The more I read, the more I looked, the more I liked. I moved to the Olympus system, and very much like it! Would never go back. Their size — notably with their lenses — was in the range I liked. Their advantages in size/weight/cost compared to equivalent ‘reach’ in FF is dramatic. Their notable IBIS, weather-proofing, and ruggedness were very appealing, as were features such as their HandheldHiRez, In-camera focus stacking, ProCapture, LiveComposite options. Their lenses are jewels. AND, their image quality is to my eyes excellent. I usually print my own 17-22”, and outsource larger. Truly can not see much if any difference in results — even side-by-side in the gallery. Have never had anyone comment on or inquire what equipment I was using. Much has been made of the M4/3’s inherently greater DOF and diminished bokeh, etc.; but, to me that has been a non-event. In fact, the reverse has been true. For example, I recall often wanting/ needing to use a wide aperture on my Nikon for low light situations, but when I set the aperture wide open to 1.4/2.8, the DOF was too thin, so I had to stop down anyway. On the Oly, it has been an advantage to have the light capture of an f1.2 or 2.8 or even 4.0, but with the DOF of about f/2.4,5.6 or 8.0. Think “f8 and be there” — but with the light capture of f4. There are other ways to increase bokeh when needed. And — a small, very subjective point — it is great to have a superbly competent but relatively quite-smaller camera/lens always with me, and it doesn’t feel like I’m pulling out an oversized tool to do a job or simply wander about. It’s just more fun. And, it’s led me to better images. Sorry for long answer to your short question. Hope it’s been helpful.