I know you know more than me about them and that's got to be a better start than I can give!
The drop down menu for subscribed communities isn't there on Hive.blog, only Peakd I think. Not sure about the other front-ends... or should Peakd be the only one that exists? 😉
Lots of specialist front ends (on a per community basis for example) is good XD catchall ones like hive.blog and peakd will just have to do what they can to be attractive.
Looks like you have to post from the community page on hive.blog.
what a nuisance XDYes, you do and yes it is. Hence why I sometimes forget to post the HomeEdders curation in there. Easier to keep the account logged in on a separate front-end, though.