Amen. The small group dynamics that has the most weight is the small group of players, not characters.
Likewise. Have done it with some frequency.And yes, I would have no problems joining an existing group with a new character. And if that group was starting a new campaign, it would seem like an ideal time to do so.
In my experience, this isn't that much trouble. One's Own Mileage May Vary... becoming unhappy with their characters. {snip} If it does, there is little problem either switching the character or, if it is the build only, to give it an overhaul.