I did not have the time to read this whole thread. On my vehicles I have run patched tires down the road for 1000's of miles at speeds that I am not going to confess to on here.
It depends on where the hole it. If it is on the face a well installed patch will run the life of the tire.
Never heard of this "plug and patch" thing. Around here the patch it inside the tire and send you out the door.
They used to do a plug too if you wanted. It depends on the tire and what you are using it for. The used to do a lot of plugs but, I haven't seen anyone try to do one in years. I don't think modern tires and plugs go together very well.