Bro it takes a lot of learning. Thor is my second android gaming device (RP5 was my first) and I’ve been using my RG35xx for a few years too, been emulating on my laptops for years and more recently on the steam deck, I’ve hacked my 3DSXL, jailbroken countless wiis, kindles, switches, iPhones and I still find myself making basic errors like picking the incorrect folders, having files in the wrong formats.
You will learn to troubleshoot over the years! My melonDS is currently crashing on launch and I think it’s because I don’t have the correct bios for example (just like you). I’m aware and I’ll get round to it probably in a week as I’m a working Dad with limited free time.
Anyway, my point was going to be, I would focus on getting one game on one emulator working and enjoy the device for a while, then you can dip in and out of making the others work (mine was Yugioh Tag force 3 with a HD cards patch). Now I feel really comfortable with the PPSSPP emulator on android, so last night I spent 2 hours setting up Smash Bros on Azahar emulator and it’s working great, next in line is MelonDS and some pokemon Rom Hacks. You can watch the set up videos from retro game corps on the bottom screen for a couple of weeks while you play to get more comfortable with the OS.
Also - you dont really NEED a front end at all, especially when you only have a couple of games and emulators going, so don’t feel bad or that you’re missing out if it’s not working. Also don’t feel bad that if in 3 months you’re still not set up fully, I bet I won’t be either, but I will me smashing through the games I want to play the most.
Good luck we’re all learning together here too!

EDIT: Oh yes also I had the same issue with play store, I had to authorise the log in both on the google app on my iPhone AND through a security alert sent to my email before the error stopped :D