Pads/disc will rub if it's not set up properly...but so do rim brakes.
TBH, rubbing rim brakes is generally a doddle to fix, 30 seconds with a couple of allen keys and you are done until you next do a major change.
Rubbing discs can be a pain in the arse and take ages to fix involving draining oil, jiggling and lubricating pistons, swearing at things until its done, then popping a wheel out and back in again and you have to start all over again. (dependent on the actual model/brand of brake.)
Sounds like you've only ever used Avid brakes
kidding, by the way). Once you've properly set up a set of disc brakes, it is, IMO, easier than rim brakes. And rim brakes aren't hard. As parsnip said, you loosen a couple bolts, give the lever a couple squeezes, and then re-tighten the bolts. In my experience they stay drag free pretty much from then on. My Shimano mtb brakes require no more service than my Dura-Ace brakes.
Bleeding them can be a pain at first, but it's honestly not that bad once you've done it a couple times. In the last 2 years, I've bled my XTR brakes once, and that was because they were setup poorly from the shop.
As far as hubs go, I would be very surprised if it's much different than mountain bikes. Front hubs will stay 100mm, some will be normal QR, some will be 15mm thru-axle. 110mm front hubs aren't very popular, I highly doubt it'll catch on for road bikes. It appears that rear hubs will bump up to 135mm, I'm sure some will try and get 130mm disc frames to catch on, but I don't see that happening. There are HUNDREDS of 135mm disc hubs. 142mm rear thru-axle's is a possibility, but I don't see that catching on with road bikes any time soon, but who knows!