You could test, if disabling rewind function brings performance gain.
Apart from that, did you test with different Emulator Cores? You can change them in ES, Game Settings, Advanced, PS1 and then change Emulator to Libretro and choose another Core if available.
And you could test, if changing RetroArch settings give you better performance (while in game, press Hotkey + B (or X on Playstation-like Controllers)).
Which version of Batocera do you use? x86_64? Did you already test with x86 (without _64)? And did you try older versions, like 5.11 or 5.18 for example?