Separating two AppleIDs?

Most of the questions I see here regarding AppleIDs are asking how to merge them or share things between them, but I want to do the opposite. 

I use two Macs (a work MacBook I don’t own, and my own personal MacBook Air), and I log into both with the same AppleID. That AppleID is my oldest one (going back to the “me.com” days), which I use for everything but iTunes (photos, contacts, and calendars mainly). I have a second AppleID that I use only for iTunes. 

But I’m uneasy now about signing into both machines with the same AppleID (that, and new security measures at work are screwing with the syncing/workflow I’ve been using for years). Is it possible to start using the 2nd AppleID for the work machine and use the 1st only for my personal machine? Maybe I'd start fresh with new calendars, contacts, etc. for AppleID #2?

I used AppleID-2 to set up “Family Sharing,” a while back, and AppleID-1 is a “family member”; does that mean I could share calendars when I need to, in addition to app purchases? Or would each ID just subscribe to the others' calendars?)

Should I create a third AppleID for work-related stuff only? That seems like a recipe for confusion.

I’d appreciate any advice.