I’ve found scans of old game guides on archive.org, and you can still check out gamefaqs.gamespot.com for walkthroughs, many of which are just .txt files that you can save and/or print.
I have an RG353V. I got that one for the aesthetic (looks like an old gameboy), and I do like it, but I can see why people generally suggest a model with a horizontal form factor instead, since the vertical (gameboy shaped) is not very ergonomic. I mainly stick to 8 or 16-bit games. but it should be able to handle 5th gen consoles (saturn, ps, n64) just fine, but 6th gen (dc, ps2, gamecube) will depend on what game you’re running and may require tweaking the settings. ps3 is right out, I’m afraid.
Like I said, I mainly run older stuff, so double check what I’m saying if 5th and 6th gen games are important to you. I don’t really mess with those.
If you want a handheld, Anbernic makes some good stuff. anbernic.com They do tend to load the SD card up with games beforehand, but the card is cheap & likely to fail, and the games are sorted & titled strangely (and may be otherwise dodgy). So you probably want to replace it with your own card with games you sourced yourself.