No idea on question 2, sorry. However on question 1:

I love wireless Carplay on my VW. Some report it to be glitchy with dropouts and connection issues, but I've never had this. I find it's really convenient to just hop in and have it automatically connect a few seconds later by the time I've put my seatbelt on and not have to have wires everywhere (first world problem I know).

That said wireless Carplay does chew through the battery, although my car has wireless charging so this is no biggie. Additionally the combination of wireless Carplay and wireless charging can sometimes cause the phone to get quite hot, and once after a long trip of a few hours the phone was complaining about needing to cool down.

Personally I prefer wired, as that way your phone is charging while it's plugged in.

Yes you can use YouTube Music, I did a quick Google and it looks as though it's one of the few supported CarPlay Apps.

Not sure if you know, but you don't actually install anything on to the CarPlay unit itself, it's all done on your phone, but there are only a handful of Apps that support CarPlay (for obvious safety reasons).

Best option is to use a head unit that provides both wired and wireless options so you have a choice. I only have wired and that's fine by me. I don't have wireless charging in my car and the ~50min commute to and from work each day is the only time my phone is charged.

For short journeys, wireless works fine and is more convenient, as you don't need to get your phone out of your pocket.

For longer journeys, it makes more sense to plug in and charge the phone at the same time.

I use an AAWireless dongle to add wifi Android Auto support to my stock headunit which only supports wired connections. Wireless adds a little bit of latency, but its not very noticeable.

You can think of CarPlay and Android Auto as being a bit like Remote Desktop for your phone. Apps that you want to use are installed on your phone, the phone streams video to the car's head-unit and the headunit streams touches and other events back to the phone. If you have an Android device, you can install the Android Auto app and run it without a head-unit connected to see what the functionality is like.