Change M365-Orga to Hybrid Orga

[aeph]

Hello,

We onboarded an M365 organization about a year ago and this organization now also wants to onboard an OnPrem Exchange.

Is it possible to switch an M365 org to a hybrid org? Or does it make more sense to additionally create the orga as an OnPrem orga? What about the license count? Can we find out which licenses are consumed online and which are consumed onprem (report or something)?

What are the advantages and disadvantages? I cannot find that much information about this topic.
An alternative would probably also be to back up the OnPrem with VBR. What would you recommend?

BR