No matter which sort you use (except for new),
Yes, sorting by new is best. The rest of the post seems irrelevant.
I wish the web ui (and apps) could work like an old fashioned usenet reader, where it would list your subscribed communities and say how many unread posts each one had. I don’t like having all the communities jumbled together. That seems fixable.
It works fine for me, everything else is worse.