First step should be to get a better SD card. The ones that Anbernic at least ships with aren't great and have a high failure rate.
I have the repo of roms from reddit saved and can share it when I get back home if you want access to pretty much every game made up until modern gen. Although you won't be able to run much past PS1.
I haven't played with any Android based SBC emulators but mine all run a stripped down version of Linux underneath RetroArch and just a snazzy UI on top. I think Android ones are pretty much the same.