I went through an ebook (Great Courses) by a Nat Geo photographer named Joel Sartore. He recommends leaving the WB set for daylight at all times. I've been doing this, and adjusting it in LR/PS when I need to. Good results. I don't know about other softwares.

That's pretty interesting about flourescent lights cycling on and off. I think I got bit by that once, now that I know what it is. Power lifting meet, pics were all over the place. Fortunately I don't shoot in that environment very often. My D-810 doesn't have that feature.

The D500 also has "Flicker Reduction", which can be helpful for more accurate exposures under some types of indoor lighting, such as is often used in gyms.

It's been a problem for sports photographers forever. The shutter speeds we need to use to stop action don't work well with fluorescent, sodium vapor and some other types of lighting that cycle on and off very rapidly (60 hz in the U.S., 50 hz in Europe). If the shutter opening and closing in a fraction of a second happened to coincide with the lights' peak output.... all was good. But if it coincided with their "off" state, things got ugly!

Flicker Reduction, when it's enabled, detects the rapid cycling of the lights and times the shutter release to coincide with the peak output. Without this feature, shooting under those lights it wasn't uncommon to see half or more of your images underexposed.... some images were underexposed to the point they were totally unusable. The only "solutions" before this feature were to use a slower shutter speed, which didn't work for sports photography, or just take lots and lots of extra shots to be sure at least some of them are usable.

I've seen a huge difference using the similar feature on more recent Canon (all current models except for the most entry level T7, I think)..... It's only very rarely that I now see an underexposed image due to the lighting. I was worried that timing the shutter release would cause delays... but it's usually not noticeable Only very rarely do I notice that there seems to be a slight delay or that frame rates slow a little during continuous shooting.

Give it a try. I know the D500 has it. I think the D850 is the only other current Nikon DSLR which has the Flicker Reduction feature. I don't know if Canon or Nikon mirrorless have it, or if some do, which models.

Maybe the lights in the particular gym you're shooting weren't a problem. Just be aware of that feature, which you might find very helpful!

Glad to hear it's working so well for you. I think there are reasons to step up from the d7100 although it's a great camera--but it has limitations.

I recently made a similar jump from the d7100 to a Sony a7iii. My first big shoot was the senior volleyball olympics in Albuquerque. Wow what a difference--I'm sure it was similar to your experience with the d500.

My point is not that either of these cameras are better than the other just that sometimes a GAS attack when you're really trying to improve a shortcoming of your present equipment works out very well. Wish you more continued good shooting.