iCloud and different Apple IDs
My current set up for my iPhone XS, MBP2010 & iMac 2020 is :
Apple ID A for iCloud &
a different Apple ID B for media & purchases (including iCloud storage)
a. Does iCloud back up all contents (mail, messages, photos, music, apps etc) from my devices? Or does it only back up those associated with the Apple ID B which I use to purchase iCloud storage.
b. My daughter is set up for family sharing on Music. She previously used mine on my phone. Would she be able to transfer her play list from my subscription?
c. My current iCloud storage is 2TB. Apple One family plan only has 200MB; which means I will need to pay extra to increase iCloud storage capacity. Will having 2 sets of storage (one on Apple One & the other on 'extra' iCloud) cause complications in backing up.
In short, is it better to just have one Apple ID???
Thanks for your advice in advance