I have a Retroid Pocket 3+ and an Ambernic RG351v.
The RG is a super Game Boy looking device that handles 8-16 bit very well as well as PlayStation 1 (if you can read the text). Runs Linux and I have a few Linux and DOS Box games installed such as a port of Commander Keen (Genius) and Epic Pinball as well as WinXP Space cadet pinball just cause.
The RP3 is a widescreen Android device that does that + PSP/Dreamcast/Saturn/N64 very well and some GameCube and PS2 (it’s picky). Also it’s android so native Android games can be played on it as well to an extinct. For some reason it won’t let me install the Android versions of Doom., But it can play CoD Mobile.
Honestly I would recommend the RG3XX for the low cost end as you don’t need that analog stick much and RG3+ on the higher end. If you need more, steam deck although you ain’t fitting that even in a JNCO pocket.