I am looking for the process to migrate ressource mailbox from exchange on Prem to Exchange Online, is it the same process that a mailbox? Do you know restrictions about this process?
Yes the process is the same. It is actually the best process for creating new resource/shared mailboxes in O365. There are some issues and limitations about creating them in the cloud and converting them. I'm hoping that microsoft will fix these. (Rather technical thread about this issues - with links to work arounds can be found here: https://techcommunity.microsoft.com/t5/Exchange/Fix-Syncback-attributes-for-Exchange-Online/m-p/3952...)