If you are not sure if board would be supplied with 12v or 24v and want to allow both without any change, may use a 9v regulator, where 9v is good enough to run mosfets gates. Also 9v would be perhaps better to run arduino from instead of 12v, coz will have less drop and the arduino regulator should be just a bit cooler. If it draws 1A (not realistic but for the math), with 3v difference thats 3W less dissipation. And for gates 9v is still plenty and fast enough probably difference is not more than a decimal point.
I mean with a 9v regulator you dont need to say :if 24v then install regulator or change jumper...", you can just say "use 12v or 24v or whatever, doesnt matter".
I mean with a 9v regulator you dont need to say :if 24v then install regulator or change jumper...", you can just say "use 12v or 24v or whatever, doesnt matter".