If 2 is good 16 is much better, and only $30.

https://www.newegg.com/p/0D9-00YZ-00002?item=9SIB4XMJ0R8505&source=region&nm_mc=knc-googlemkp-pc&cm_mmc=knc-googlemkp-pc-_-pla-hoowan-_-solid+state+disk-_-9SIB4XMJ0R8505&id1=2084569190&id2=72044596770&id3=&id4=&id5=pla-1656761138292&id6=&id7=9030019&id8=&id9=g&id10=c&id11=&id12=EAIaIQobChMI4P-mtYS39wIVzMDCBB2zAA9NEAQYAyABEgIazvD_BwE&id13=&id14=Y&id15=&id16=375187497489&id17=&id18=&id19=&id20=&id21=pla&id22=505517545&id23=online&id24=9SIB4XMJ0R8505&id25=US&id26=1656761138292&id27=Y&id28=&id29=&id30=7777475936976365781&id31=en&id32=&id33=&id34=&gclid=EAIaIQobChMI4P-mtYS39wIVzMDCBB2zAA9NEAQYAyABEgIazvD_BwE&gclsrc=aw.ds
--Bob

I have a Rokinon 8mm f3.5 that I have had for several years and I love mine. When I bought it I used a Canon T1i and I was never disappointed with it. I have also used it with my 50D and now my 90D. Yes they are all crop sensor and just maybe that is why I am so happy with it. If I use it right I don't see all the distortion you might expect. In fact my wife, who hated pictures taken with fisheye lenses most often didn't know she was looking at those I took for her. I also have several other "Cheap" lenses that I have enjoyed for years because when you don't have the cash for the expensive things many of the cheap lenses and other camera things works just fine.

While the Rokinon lens would certainly work well on your 90D, I'm not sure that's the best choice. It's a full frame lens and yours is an APS-C camera.

Canon EF-S 10-22mm f/3.5-4.5 USM and EF-S 10-18mm f/4.5-5.6 IS STM are both excellent optically. The more expensive 10-22mm is both faster and better built, while the 10-18mm is a real bargain, has image stabilization, but is a bit plasticky and not quite as fast focusing (although you will see little difference in speed because ultrawides like these hardly need to move their focusing elements at all to go from near to far or far to near).

However, the Rokinon lens is manual focus only... while both the Canon lenses have excellent AF systems.

Rokinon SP 10mm f/3.5 for Canon EF......... $899
Canon EF-S 10-22mm f/3.5-4.5 USM......... $649 (plus $35 for Canon Hood EW-83E or $10 for Vello hood)
Canon EF-S 10-18mm f/4.5-5.6 IS STM..... $299 (plus $25 for Canon Hood EW-73C or $12.50 for Vello hood)

Prices are for new (at B&H). Both the Canon lenses have been around for a while, so it's pretty easy to find nice used ones for a bit less money. They also may show up refurbished at the Canon website (same warranty as new).

The Rokinon has a convex front element that precludes using standard screw-in filters. You may be able to get a specialized clamp on filter holder and square filters for it, but those typically cost around $300 for the holder and a couple filters. In comparison the Canon 10-22mm uses standard 77mm filters, while the 10-18mm uses 67mm.

Note the hoods for the Canon lenses are not included, are sold separately. Because of it's built-in lens hood and convex front element, the Rokinon lens uses a special lens cap. The Canon lenses use standard caps.

If you were using a full frame camera, the Rokinon 10mm lens would be a good choice. But since your 90D is an APS-C camera, either of those Canon ultrawides would likely be a better choice.

I've been using the Canon 10-22mm for a five or six years. It's an excellent ultrawide. Sharp and one of the most flare resistant of all the ultrawides. My only complaint is that the hood is quite large... but I still use it because it works.

I'm not knocking the Rokinon lens. They're quite well made. In fact, I've got a different Rokinon lens that I use on my Canon M5.

You can probably find some reviews of the Rokinon lens on YouTube.

Check out The-Digital-Picture.com for very thorough reviews and extensive testing done with the Canon lenses. Bryan extensively reviews Canon gear, as well as some others. He has done test shots with the Rokinon 10mm, but has not done a full review of it. Plus, the test shots with it were done on a full frame, 50MP 5DS-R... making them somewhat hard to compare to an EF-S lens on an APS-C camera.

On your 90d, it’ll appear as a 16mm field of view and would likely show distortion at close distances. Manual focus, as well, indicates to me that it will be best suited for landscape shooting, where you can set focus at infinity. So, stopped down or not, unless you shoot with a shutter speed better than 1/200, I suggest being on a tripod. I owned a used Rokinon fish-eye for a while and was generally pleased with results…..but, to be honest, quickly grew bored with it and was happy that I purchased used rather than new. I’m thinking you’re interested in the lens for more curiosity than function, so I definitely recommend you shop the used market. All that said, it’s reviews from users is fairly positive, so if you buy, enjoy!

PassMark on your AMD CPU is 10% faster on multithreaded tasks (2 more cores) but ~20% slower on single thread tasks. As far as the GPUs, their PassMark speeds are almost identical. And if you read the Dell specs, there are 2 DRAM DIMM sockets, so he can add another 16 GB.

But here’s the question. The OP is obviously not a computer savvy nerd like you or me, so what does he do for warranty and support? (And I notice you’re not including an OS). You need to sell your components to someone who is comfortable building their own machine, installing their own OS and going to the individual component mfgs for warranty work after diagnosing the issue, and that is NOT the OP.