So is this why the changes in the RetroArch confg are never saved for the P2 bindings? Do I need to change that line in the Python script to remedy this? If so, where do I find it?

It doesn't matter overly now though - I've manually set the emulators for the few games that can get by on the other emulators (despite the save game location being different to proper "save" folders!). I've yet to decide whether to use this method or my manual config file.

I think if SNES 9x could be setup to only enable multitap when 3+ controllers are connected, it would be perfect. That and the save locations for the other emulators.

Other that that my setup is god to go. Thanks guys

@Substring I added input_libretro_device_p2 = "1" to the retroarchcustom.cfg.origin file. Doesn't work. SNES games still see the multitap.

Hmm. This custom file obviously overwrites more than I'd like - now disabling the emulator menu only works for non-SNES games.

@Substring the retroarchcustom.cfg.origin file doesn't have the input_libretro_device_p2 line to edit.

I may have cracked it!

I noticed that, when saving a new config from within the retroarch menu, it was saving the file to a hidden folder... /recalbox/share/system/.config/retroarch/config

I copied this to the /recalbox/share/system/configs/retroarch folder and uncommented and edited the below line in the recalbox.conf file...
snes.configfile=/recalbox/share/system/configs/retroarch/snes9x_next_libretro.cfg

All loaded well and the multitap config remained.

Then I decided to just copy the retroarchcustom.cfg file to retroarchcustom2.cfg and edit the below line...
input_libretro_device_p2 = "1"

Then changed the recalbox.conf file to reflect this...
snes.configfile=/recalbox/share/system/configs/retroarch/retroarchcustom2.cfg

All seems to be going well so far.

I'm not sure of the repercussions yet, but it's a good start.

So, it looks like the retroarchcustom.cfg file is bring saved back on exit. Setting the "Mex Users" to 2 holds it's value, but the input_libretro_device_p2 value always reverts back to 257, even when setting this to SNES Joypad within the retroarch menu.

This is clearly being overwritten from somewhere else.

Roger that. I'll wait for the heroes

I'll continue to poke about in the mean time though - I can re-install everything if it breaks. Will post back if I find the cause of the issue.

Have also tried setting input_libretro_device_p2 = "257" in the retroarchcustom.cfg file to input_libretro_device_p2 = "1" but it just reverts back as soon as a game is launched.

There must be an easier way to disable multitap for Snes(x - I know it wasn't the default mode before Recalbox v4.

Even the retroarch-core-options.cfg file contains the multitap = "disabled" option.

Already have. It appears that all other options are sticking except that one. The other options under the "save on exit" also hold their values, as well as setting the max number of controllers to just 2. But, with every launch of the games, the Player 2 binding always has the type set to "Multitap".