My basic set-up guide for buying a desktop/tower based FS system.
Start with the monitor first then build from there.
Is something basic like a 27" LCD flat screen running at 2K between 60-120 Hz going to make you happy?

Maybe you want something larger? Keep in mind that as your display gets larger or you switch it up to 4K or maybe VR, your GPU requirements get more expensive,
IF its even available. Do you have the room for a billboard-sign sized 4K wall of light? More pixels may need a bigger/better GPU which also drives your choice of power supply and load-out of RAM. This might be hard to realize BUT bigger power supplies usually go hand-in-hand with the longevity of your basic hardware. Also important- digital electronics DO NOT get along well with liquid cooling.

If it has fluid in it, it WILL eventually leak. One last consideration, whatever computer you decide on- it will need some periodic maintenance. How MUCH maintenance it will need should drive your choices. Blowing out the dust bunnies twice a year and replacing the CPU battery at least every two years is MY kind of maintenance.
Now, forget FS for a minute. What
else are you planning to watch or play? Just forum surfing and maybe a couple of streams and YouTube? Movie night with Netflix or DVDs? If you build-out a full cockpit sim, do you
REALLY want other people to see it? Adults seeing their first in-house game room will revert to being children faster that you can say "WHOA..". What their eyes see
will make their hands yearn to touch. Are you friends enough to laugh off a broken controller or custom throttle quadrant?

Do you have a Man Cave with a "Keep Out" sign on the door or does all of this gear have to blend into your dinning room/tv room/basement? Will your spouse/partner understand
why there's 1-to-1 scale F-16 cockpit in the bed room?
My basic idea is to not over-commit
before you go shopping. Have a clear idea of what you NEED more than what you WANT.
Next, pick out your rig based on what you're planning to play.
"Future Proofing" mostly doesn't exist right now aside from picking out your CPU.
We're kind of stuck buying what hardware is available. Stuff like RAM and storage have gone thru the roof thanks to Data Centers and Crypto.
If your plan is to play FS2002 to FSX plus some CFS, do you
really want that i9 CPU? Sure, it wouldn't hurt but do you even NEED it?
Old games are single-core games and single core games depend on (stock) clock speed. Period.
Are you watching someone play something on YouTube or Twitch and you
really want to play along?
Realize that a lot (almost all) of that content is EDITED to some degree.

Meaning, it takes work to upload that video.. AND hardware, AND a lot of time.
What you really want to avoid is that treadmill of BUYING HARDWARE just to play ONE game.
What you're doing is burning $2,000 to play a $60 game. Does that sound like something that makes sense??
You could justify it back in the "00's" up until about 2015. Defiantly NOT NOW.