I'm not aware of any documentation that shows the permissions required to perform specific operations in the SharePoint APIs so I can only give you my opinion.
I think of it this way:
- Read is roughly equivalent to visitor permission
- Write is roughly equivalent to contributor permission
- Manage is roughly equivalent to owner permission
- FullControl roughly equivalent to admin permission
I say "roughly equivalent" above because I've come across scenarios where I was sure I'd only need Write permission but it turns out I needed Manage or I was sure I would only need Manage but it turns out I needed FullControl. I've found that determining what permissions are required sometimes comes down to trial and error.
In regards to the Get-PnPTenantSite cmdlet in PnP PowerShell, it is used to connect to the Tenant Administration site so it makes sense to me that Read or Write permission would not be sufficient.
I hope this helps.