Well it all depends, but if you want to trigger a note - like you’d do with a keyboard - then it is a… note. CCs will help you modify the sound, but you could mute/unmute your sound this way, which could be heard as a trigger as well (although it isn’t). If you want METRO to trigger notes, then put METRO/VAL to 127 for max velocity (or whatever you think is best) and send it to MOUT_NOTE/VEL, after choosing the note you want to target in the INPUT section. You might find out that it’s sending one note once and nothing more (haven’t tried myself this way so I assume it’ll be the case), because it’s only sending 127 all the time (so no “note off”, or VEL=0). If so then you can use a TOGGLE object: put the value of the METRO to 1 again, and toggle between 0 and 127. Your tempo will be divided by two (you’re sending a note each second beat), but it’ll hopefully work.
Oh, and the scaling is just from 0 to 127 for everything using MIDI - also to pick a note, as that represents about 10 octaves (10 times 12 semitones) and half. That corresponds to an ambitus going from 20 Hz or less to above 20.000 Hz, so all you need is in here. Finally if you want to go from CV to MIDI you’ll have to calibrate: find the minimum and maximum you are receiving (for instance with a Koma Kommander I get values between about 80 to 3100). Remove the minimum (SUB 80), multiply it as much as you can so you get close to 32767 (MUL 10), mostly so you get more precision when dividing in the end, and then divide to get a number going from 0 to 127 if possible (DIV 237). Now the Commander can control any MIDI source from 0 to 127, sending to CC or to notes/velocities with as much precision (meaning not much, but well) as MIDI can offer.