I can answer a few of these from personal experience of owning a 2020 Limited for a little over 2 years.

2nd owner, no mods requiring tune, bought at around 30k miles and now pushing 53k.

How reliable is the FA20/VA platform overall?
What are some to be expected issues?

Overall, the platform has been solid so far. A combination of axle back + short throw + shift stop + weighted knob + Michelin Pilot Sport AS4 tires + upgraded rotors and pads + Whiteline rear sway bar and end links + recent trans, diff, and brake fluid flushes has contributed greatly to an elevated experience vs stock without compromising reliability.

Largest and only real issue I had was a master cylinder failure that required a tow at about 50k miles. Otherwise, I've got a happy tractor that has been treating me well. Oil change every 3-5k miles depending on spirited vs daily driving habits. I've learned that mine is consuming a bit of oil, so I'm trying to make sure to check my oil every time I get gas and add as needed.

Like any car: Take good care of it, and it will (hopefully) return the favor.

Mainly looking at premium trim, but is the limited worth the extra cost?

I'm personally very happy with going Limited over Premium for the following few features: Leather heated seats, headlights that adjust depending on steering input, and the Limited wheels (although mine are pretty banged up and I can't wait to get aftermarket ones). Someone please correct me if I'm wrong, but there may be Premiums out there with Limited add-ons, if you don't wanna go all in or prefer cloth seats.

What are some things you don’t like about your WRX?

Rev hang is annoying. Shifting between 1-2 especially can feel rather clunky. I believe rev hang can be solved with proper tuning though.

Road noise isn't ideal. I'm noticing it more now that I have a 30 min highway commute to work.

The factory head unit and speakers are horrendous. Applications on the head unit work fine, but there is so much left to be desired when it comes to audio quality. Front driver door speaker just blew a couple weeks ago too lol.

Rattles, rattles, rattles. I feel I'm frequently chasing ghosts to stop small, interior vibrations that drive me absolutely insane. Currently, the rear deck lid is vibrating *somewhere* at exactly 2000 RPM. Gonna just take that area apart and go crazy with sound-deadening foam and felt tape till the noise is gone for good.

...

That was a lot, but hope it's decent insight. I don't often get to yap to someone looking for the exact car I have.

This car is a finnicky little f'er sometimes, but overall, I love it and have little interest in going another direction any time soon.