Most people sitting in cities are usually idle, in city spamming their junk items for sale or arguing something in chat, or at the auction house.
If you want interaction with other players, you pretty much need to be playing the current content. Most other places are gonna be dead.
I believe BfA has a single level 110 boost to jumpstart you into the current content if you don't want to explore old zones.
However, being that it would be your first time around, do whatever you want to do.
I believe you can also make level 110 trial characters to test them out before deciding you want to use your boost for that race/class.
You can also purchase additional level boosts if you already used yours, want a new character, and are too lazy to level it up from scratch.