Hi,
For Mgmt backup/mds backup is enough
For maestro devices the recommendation is snapshot
MHO- for MHO we don't expect a lot changes there, at least you add/remove SGM interfaces, if not you can have 1 per month
for Security Group collect the snapshot from SMO, you don't need the snapshot for each SGM, since they are cloned from SMO. so log on local clish to SMO and create the snapshot.
How ofter? well it is depend of your need, if you have editions like SGM, interfaces/routes/arp frequently, then maybe you need per week, but if the only changes are policy, you even revert an old snapshot and push policy. this apply regular for non-VSX.
if you have VSX, you have to have on same frequent mgmt and security group. since the database on both side have to match.