Hi! First post. Been playing modular for about a year, but guitars and synths for about 25, yikes! Jumping into modular I knew off the bat I’d be using guitar pedals, because I didn’t want to rebuy that stuff again for the rack, and I still play guitar a lot as well. The only really issue is the levels, which has already been mentioned. Sometimes you will distort the input of the pedal. One of the easiest ways to manage this is to send the synth level into a mixer that has aux sends, almost always in this case that I’ve managed to alleviate distortion this way. I don’t think you really need those fancy out modules for Euro, you can get a cheap Behringer mixer for under $100 that has aux sends. If you want to stay in the rack, the Pittsburgh System Interface has worked for me so far. I’ve found that the Eventide H9 handles levels well too, and sounds great. Other pedals I dig with the modular are MXR Carbon Copy Deluxe, has lots of options for synth integration such as a line-level switch and dry only switch, and even clock syncing!