I have friends with various Miyoo and Anbernic form factors and they are basically all decent for emulating everything up to 16bits. 32/64bits are more hit and miss. Something like the Retroid Pocket 5 is much more powerful, but costs like 5 times as much as most Miyoo/Anbernic models.

I have an Anbernic RGCubeXX which is great for vertical shooters and square screens (think OG Game Boy).

If you want to emulate up to PS3 or PSVita, the Steam Deck is unbeatable.