The last couple of updates have drastically improved the stability of the emulators! None of them have a desyncing issue with the screen, so I can play Sonic 1-3 without feeling nauseous. Seiken Densetsu 3and Mother 3 now run at 60fps! However, Kirby Super Star now kills the emulator for me, and when it doesn't, it chugs at 0-1 fps at the title screen. n3ds 9.9.
Honestly not much has changed in the cores or RetroArch itself after aliaspider implemented VSYNC and aspect ratio switch so I dunno what could cause improvements or slowdown






