Hi,
It depends on various factors. There is no straight answer here.
If you provide below answers it can give more clarity.
1. Is your current SQL database compressed, like page compression is done?
2. Is you single Production DB 5TB or all in combine.
3. How many and how long outages can you take?
With the DB size and assuming DB is page compressed, I would say below you perform in place DB and EHP upgrade before moving to cloud. This reduces unknown risk as issues related to DB upgrade and EHP gets resolved beforehand and you know any issues which occur are related to hardware changes once you move to cloud.
Doing all after moving to cloud may mean a big outage and to many variables.
Another way could be to move as is to cloud and come to a steady state and then do DB and EHP upgrade as separate projects
Thanks
Imtiaz