actually all midimix configs (scroll down) use scripts with the same name with partly different content.

HOW TO : portable or parallel Config

Portable : make a portable installation via installer and
import the config file in the started portable instance

Parallel Config : Create a folder and start REAPER with Parameter -cfgfile "insert the directory path to a reaper.ini here"
like -cfgfile c:\bla\bla\reaper.ini
maybe you create this directory before and put your REAPER Licence file into it.
REAPER will scan the fx while installing, if you get a chance to cansel that, do so. my templates
uses empty vst-search-paths anyway.
run after installatin and drag the Config.template into the reaper window (windows) or import it via the preferences.

the templateshas it all.. the assigning of midimessages to those scripts will vary per config then.

for all configs it is necessary to plug th MIDIMix in (obvious) and
set it in the Preferences for MIDI Input active in input, all and control
and in the MIDI Output : enabled and as Index 1 (right click the index to change)

the scripts use stuffmidimessage with fixed channels. In windows mine would set nearly like this

the configs should include that already , but.. never knows what borks a config

midimix_3_knobs_4_fx_recarm_noosc (NO OSC)
midimix_3_knobs_3_fx_recarmforsynths (NO OSC)
midimix_3_knobs_recarm_mutes_items_on_track (NO OSC)
a testversion with switchable recarm_scripts
midimix_3_knobs_recarm_all_in
midimix_3_knobs_recarm_all_in_4

midimix_3_knobs_4_fx (OSC)
midimix_3_knobs_4_fx_recarm_ktb (OSC)

and stuff with realearn for the MIDIMix
midimix_and realearn

and then this
midimix-scripts in reapack
and remember : If you are not a daw pro after learning -beep- reaper then, you know, there's something wrong with you"