My set-up is similar to what you are considering. It’s taken me a while to settle on the optimal routing situation but I feel like it’s pretty dialed-in at this point. I’ve got an OT, Push 2, and a few other pieces of hardware with their own sequencers working together tightly. So - Push 2 is the “master controller” so to speak. Live is the master clock. I tried using Live as a slave, but was never satisfied. There’s a little jitter (USB midi), but since the overall sync is tight, I live with it. If I added an external sync device I think it would be perfect.
For midi, Live clocks the OT, and the OT is set to receive AND send clock. The OT clock then goes back to the midi router (iConnectMidi4+), and clocks the other devices. In Live, the offset amount in the midi/sync preferences is set to a negative value that gets the OT and Live audio tightly in sync. The audio from the devices clocked by the OT are also synced with Live, since they are driven by the offset clock from the OT. The iConnectMidi4+ is flexible so I route note data in such a way that any instrument can send notes to any other. So Push 2 can send to the OT or any other HW instrument, OT can send to Live or any HW instrument, and Live can send and receive from anything as well. Individual midi tracks in Live are dedicated to a single HW instrument, and each of these has a unique negative Track Delay value entered, to get notes sent from Live to record correctly into that specific instrument’s sequencer.
There is no HW mixer involved, everything is monitored through Live. I have HW going into the OT and the OT into my audio interface, but routing stuff directly into the interface works too. Audio in Live that I want to record to the OT gets bussed to a dedicated “audio to OT” track that also has a negative Track Delay entered, which allows for the OT to record perfect loops. When I want to record the OT, I use cue outputs, in regular mode with “cue mutes track”, so I can record individual tracks to Live while still hearing everything else from the OT.
This all works really well, now that I’ve ditched use of the External Instrument device in Live. That method was working fine until I added an iPad to the equation, and adjusting timing on one device started to affect all the others. Still haven figured that one out.
BTW: Use Delay Compensation and Reduced Latency when Monitoring are both ON in Live.