I’ve been following the community for about 2 years now. Started with a Retroid Pocket 2+, then picked up a Miyoo Mini for something that was a little easier to take on the go, then added an Anbernic rg35xx. I still think the rp2+ (and now the recently released rp2s) is the perfect 1st device. Generally handles everything up through Dreamcast without issue, 4:3 screen, decent enough buttons, affordable.
If you want something a little cheaper or in a verticle format, the rg35xx or Miyoo Mini+ are both good devices as well. I’ve never used the Miyoo Mini+, but I personally prefer the rg35xx with Garlic os to my Miyoo Mini with onion os.
If GameCube or PS2 are important to you, just get a Deck.