Welcome, Nummies, and congrats! You're already way ahead of where I was at your stage in the pregnancy. I started out with OBs; discovered the twins at 19 weeks. Gradually got the picture of what a medical birth would be like and wasn't OK with that. Found a midwife willing to assist a twin mom at about 30 weeks, and stopped going to OB appointments around 34 weeks, although I had my last u/s at 37 weeks. Then birth at home at 39 weeks. Loved being at home!
So you're considering going to an OB in case your twins come early. Smart to plan for it, and hope you won't need any of your preparations!
Ask your midwives and Find Your Tribe forum about naturally minded OBs. There are a good number of OBs who will say they are willing to deliver twins vaginally, and some actually are, given the "right" conditions. Since you seem to want as little involvement with doctors as possible, I might recommend doing parallel care with an OB from weeks 28 - 36. That would be no more than four doctor's appointments, and would cover the early birth window.
Something to consider, and that way, should you need to transfer during your homebirth, you might also have someone to go to.
For the record, I'm not suggesting telling this OB about your homebirth, personally I think that would cause more problems than it solves. I would just claim I was transferring care to them, and then miss the last few appointments and birth at home.