is out for retorarch.. has a few issues currently (depth to rdram needs to be off , indiana jones won't boot) but it is definitely faster!!
as of today the core is on the psx classic buildbot https://classicmodscloud.com/classic_libretro/nightly/classic_armv7_a7/2019-02-09/so/Which platforms is this available for? Can I use it on the PlayStation Classic?
Widescreen mode has been available on the standalone Mupen64plus AE for quite some time now. You can set it to 16x9 or 16x10.