The iPad complicates things for me because I’m not sure how good the midi clock is. If the clock is good and tight then iPad can be master clock and go in front of the OT. Then you’ll use the midi thru on the OT to control the synth you want the ipad to control. Thats a big if though!
Master midi clock is very important in big set ups. I cant vouch for ipad midi clock. I’ll guess its not the best. You want to keep daisy chains minimal and the set up as simple as possible. Midi can be very fustating especially when you daisy chain so keep that in mind.