I'd love to figure out how to pop a wheelie or the push & pop method you describe to get over some obstacles (logs, rock steps etc). I need to practice this somehow.
I don't know about more controllable clutches on the TW, but in the beginning of the 1st video going up hill, I was feathering the clutch to keep up the rpms so I wouldn't stall. I almost killed it and if you listen closely at one point the rpm's increase quite a bit. This was me pulling in the clutch and feathering it to keep my momentum. It worked!
Of course, there are a bunch of times in my riding experiences which even though I was feathering the clutch to keep going, I still ended up losing too much momentum and stalling. In the second video at about the 2:30 mark, I tried feathering the clutch, stalled and fell over. Thankfully it was sand! (Side note: This spill was with my stock tire. At a different time going up the same hill with my Ceros, I made it. So, something can be said for good traction too!)
Sometimes it works and sometimes it don't.