conventional side by side, dual extruder machines are just more trouble than they are worth.

nozzle wiping is a bit pointless as it would always wipe both nozzles. removing filament from the one currently being used to extrude.

And no matter how carefully you calibrate them - it doesn;t take much for the nozzle not in use to catch a part of the print.

Since i switched to top mounted spool holders on the knp I just use the right nozzle.
I can still have two filaments ready to go - I just feed both into the right nozzle when i want to change.

But it's just an awful lot of hassle to use both on the same print.

Given that a decent idex can be had for less than $500 and a decent dual extruder is going to be similiar oir more. Idex is now very much a good and viable alternative.