All file managers are just applications which can be run by MSX-DOS2 (i.e. they have nothing to do with a specific flash cart per se - they can be run on anything which can run msx-dos2, some might even run on msx-dos1). Some may be proprietary (hobbyist projects still, usually), some may be freeware, some may even be FOSS (I don't know/remember all file managers and their specifics out there).
All file managers are optional in any case - they are just wrappers to make life easier, and all they do could be done from the command line (well, in principle) - but that may get quite hairy and at least quite boring quite soon. I do strongly recommend SofaRun!
If they already exist on the MegaFlashROMSCC+SD, depends on what the msxcartridgeshop chose at the moment. At least previously it included a ROM-floppy image which had multimente on it (IIRC!). It didn't autoboot to multimente, however. Things might have changed.
Sofarun is a program you can run from Multimente, so no problem there. But as an MFR user I do not use Sofarun that much since you can run/flash ROM and DSK files easily straight from Multimente.
OK, so you can't have both, do you have to choose either the pre-installed one or the SofaRun? As soon as I can save some money I want to buy the MFR!
You can have both. Just obviously only one can automatically start after MSX-DOS2 (=Nextor) (=the OS) boots up. But you can quit the one and run the other. Or don’t auto-start either, and manually start one by typing “MM” (MM.COM = Multi Mente) or “SR” (SR.COM = SofaRun) on the MSX-DOS2 command prompt. Multi Mente and SofaRun are just MSX-DOS2 applications.
