>And how should I manage my Config.fp and foxuser.dbf? It changes every time I switch the versions.


You should use a CONFIG.FPW and the standard FOXUSER files, and in your AUTOEXEC.BAT, create an environment variable FOXPROCFG, that points to a different CONFIG.FP, and references its own copies of FOXUSER:

in AUTOEXEC.BAT
FOXPROCFG = C:\DOSFOX\CONFIG.FP

In the directory C:\DOSFOX
CONFIG.FP:
RESOURCE = C:\DOSFOX\FOXUSER

This should handle this issue neatly - your CONFIG.FPW, if any, gets used by VFP, but any FPDOS session uses the special version pointed to by the DOS environment variable