I just bought an XPS 13 9360 and returned it due to the coil whine. I've never had that issue on my Macs before so once I get refunded I'm going to buy a MBP instead.
I'm in a similar boat. I'm replacing my 2013 13" Pro with a new XPS 13. It just came yesterday so I can't really review it at this point, but I'm impressed so far.
Maybe, but it may not be a huge issue. I've had very good luck using apps split-screen in Android 7.0, which has a similar aspect ratio to classic BB devices.
Since Chrome forked WebKit, it's been going downhill. For the past little while, with each new version of Chrome, I notice more annoyances and bugs. I recently switched back to Safari as well, and while it's not perfect, it's better than Chrome IMO.
My friends and I have never ran into this issue switching from iOS to Android. The main thing to do is to disable iMessage on your old iPhone before you get rid of it; that should unregister it on Apple's servers. If you do that, then you should be unregistered unless you have another device hooked up (i.e. Mac).