Im saving my money for one of these things either the retroid pocket 5 or retroid pocket classic or the miyoo a30
Miyoo a30 sucks, really. I have one it's
among the few THE handheld I regret to have bought.
My favorite is the RG ARC-D with its 4 inch screen. It's dual boot with android/linux but I removed android to install the Rocknix (linux based CFW). I don't like android and the linux stock OS is OK but Rocknix is better.
First I ever bought is the Powkiddy v90, it's great with the triforce CFW
https://github.com/TriForceX/MiyooCFW, but it's not powerful and you must shutdown the OS before shutting down the machine with the power button otherwise you get prompted with a "disk check" at reboot, and the bigger your SD card is the longer the disk check will last. Also, it's not based on retroarch, it's working with standalone emulators. You can run some PSX games like Dino Crisis for instance, but forget about tekken 3 and Command & Conquer, it's too demanding for that machine. Also, it runs on BL-5C battery (Nokia phone battery) which can be changed accessed easily but again it's only good at running anything below 6th gen consoles and few 6th gen console games.
It's highly customizable with TriForce CFW
IMO it's among the best handhelds you can have for $30/40, but nowadays you might as well go for the Miyoo Mini Plus (not tested) for roughly the same price tag.