I have a Retroid 3 plus. I'm not buying another Android handheld. They don't make any sense. You have long boot times, and if you rely on sleep it needs constant charging. A game controller on an Android phone is a better experience in every way.
I have had several Anbernics and a Miyoo Mini. My favorite is the Miyoo because you turn it on and in seconds you are where you left off. When you turn it off, it auto saves and goes completely off so the battery isn't dead the next time you want to play.
Linux Anbernics can do this too it's just the Miyoo boot time is faster.