I can't comment on your first question but can on video coaching.
While in person is always good, it often tends to be intermittent (a ski school here and there), and from a different set of eyes. Unless you're lucky enough to have access to a consistent coach in the boat. I would never turn it down. But it's just hard to get the consistency required to really make tangible improvement.
I've been sending Terry Winter video for the past 3 years and have gone from just starting skiing as a 38 year old, unable to run 30mph, 15off, to getting into 34mph, 35 off (yes I know, still quite a modest line length). So much of the progress I attribute to having a pro - that knows my strengths and weaknesses & what I'm working on - and turning that into constructive, actionable feedback I can practice and come back to him with. As such, I think having a consistent voice is good. Rather than 8 different coaches telling me different things (all very good things I'm sure, but consistency and a knowledge of what I've tried, what's worked, what hasn't, is great). In addition to maintaining a history with a video coach, what I like about video coaching is that it's highly visual. You can see your style, often side by side with a pros. You can watch it over and over. Added bonus is that I've gotten so many tips and video from him now that its getting to the point where I can watch my own passes (I record most all of them) and self diagnose the simple stuff myself. And get the much more nuanced feedback from him. Anyways. enough of the plug for video coaching but I can't say enough good things about how much it's helped my skiing.