There is an old rule about having only one powder on the bench at a time.......Just make sure you understand this.Am not commenting on how anyone "manages" their own reloading bench,just make sure you understand the why's and wheres concerning it.
To your question of multiples......our bench has
1 Lyman 55,3 Lyman pistol measures,2 RCBS.
The 55 is used for cast bullet pwdrs in rifles only.The pistol measures never get their rotors swapped out,they're for specific loads.The two RCBS measures,have sm rotor in one lrge rotor in other.These last two are the ones that get used for chasin loads N nodes.
Well theres another on the big Pacific 366,but it stays the same 95% of the time.