Apple Music: separate logins & preferences per family member
I don't know if it's intended functionality, but it appears to be working the way I want now. Here's what I did.


Logged out of both iTunes and iCloud on my devices and started over.
Logged into iTunes account on both our iPhones and Macs with old Apple ID we use for all purchases. Logged into iCloud on our iPhones and Macs with our own .mac accounts.
I enabled Family Sharing using my iCloud/.mac address and invited my wife using her iCloud/.mac address.
I logged into Apple Music with the Apple ID associated with purchases. My wife logged into Apple Music with her iCloud/.mac address used for Family Sharing. 


Once logged in, we both were able to pick our music types and artists. It looks like we were both pre-set to follow an identical list of many, if not all (245 artists) from music we've bought in iTunes over the years. But, while there were a few glitches I noticed the first couple of times I opened the app, Apple Music on my iPhone and Mac appear to be retaining all my preferences after following &amp; unfollowing some artists, and vice versa on my wife's iPhone and Mac.

In the end, it seems relatively straightforward, but it didn't work at all the first couple of times through (which may have simply been launch day weirdness) and I couldn't find any official support info that outlined if this was possible. Hope this helps someone else.