Holy crap....
I knew I had become ignorant to PC's/technology over the years , but this just proved it beyond comprehension lol.
If I can ask for an opinion, if you were to look at the gaming towers they offer, what would catch your interest? Obviously, the benefit to PC's has always been the ability to constantly upgrade, so finding a decent starting point which I could then progress might be the best route for me. Not only does it provide the immediate upgrade to PC, but that hands on aspect would definitely click my brain into grasping it all again.
Don't have to, but I am curious no doubt. I'll need to do some catching up on it all (yay internet), but for sake of learning, if I ended up, say spending $700, or even $500 on a tower, and plan to upgrade with what you've suggested from that point, is there any concern to size of the housing, or performance issues as far as compatibility with the other components?
I recently built a PC with my son after "being out of the building game" for 20 years or so (I'm a software developer and primarily using laptops which aren't quite as easy to custom build).
Regardless, I did a bit of studying up (as you mention above) and I ... well kinda fell down an internet rabbit hole for a few months.
It really isn't as crazy as it seems though; the main difference from a couple decades ago is that it's actually *easier* to build a custom computer nowadays than it used to be. Fewer overall components, etc.
Your main choice is going to be Intel vs AMD. (Main difference, *technically* Intel is faster single-core and AMD is faster multi-core. But this is fairly subjective and as you also mentioned somewhere; most people are incredibly biased on that choice. I stand by the single-core/multi-core statement though--and it is especially true of the cheaper CPUs.)
I suggest checking out the Hardware section of Rock, Paper, Shotgun to get an idea what sorts of gaming components are good for what you want.
I'd suggest also taking a look at pcpartpicker. They have some pretty good generic parts lists that fit within various budget categories. These are pretty helpful to compare against prebuilt towers too, for instance you can compare the parts lists to tech specs of the prebuilt system you're looking at and they should be pretty similar.
I'd definitely recommend using pcpartpicker to build out your component list as it definitely helps you avoid any incompatibilities. While it's true the risk of buying incompatible components is fairly low, it's good to reduce that chance as far as possible. And I also find their pricing / purchase comparison links very handy when pulling the trigger to buy everything.
Background Reading:
https://www.rockpapershotgun.com/category/hardware/
PC Part Picker - "Modest" (~$700) Builds (for Intel / AMD)
https://pcpartpicker.com/guide/t2wrxr/modest-intel-gaming-build
https://pcpartpicker.com/guide/gfZxFT/modest-amd-gaming-build
If you have a bit more to throw at it, I'd recommend a reasonable sized M2 storage drive (instead of, or in addition to one of, the SSDs in those listings).
This is what my son and I built (separated into two phases, the first one was just to get it up and running for software development, the second added a non-integrated GPU and some extra RAM/storage--the software dev I do is heavy on RAM and storage):
Phase 1 (base build):
https://pcpartpicker.com/user/tricorius/saved/#view=NRD7TW
Phase 2 (better gaming):
https://pcpartpicker.com/user/tricorius/saved/#view=ryGb8d
If you end up buying a prebuilt and expanding it further, be careful what you buy. A lot of the "name brand" PCs take shortcuts which make it a lot harder to upgrade down the line. Also, breaking it open and changing around components typically voids your warranty (which isn't probably a huge problem, as you'd probably be using it "as-is" for a year or two and by then the warranty is usually useless anyway).
With prebuilt PCs you can definitely get something that has a custom chassis or such that doesn't contain the airflow to toss a larger CPU or GPU in it; or doesn't have the space to put a larger fan/all-in-one cooler, etc.
If you have questions, toss a few links in here and I'm sure a few will jump in and give our opinions.