Still best practise to create new permissions groups on SharePoint?

[Harmanna Zoetekouw]

We are busy migrating our SharePoint 2013 collaboration sites to SharePoint Online. We noticed that in SharePoint Online, within Site Settings, the options regarding permissions are hidden (for instance 'Site permissions'). Within SharePoint 2013 we created a lot of custom permission groups to make certain libraries private. Is it still best practise to create custom groups for permission management within sites also in the modern SharePoint sites? Or will this functionality be phased out? Or a better option be introduced? 

[#2]

Modern team sites are connected to Office 365 Groups, which govern site permissions.

Best practice is to avoid altering site permissions at a lower level, using instead the Group membership UI.

Anyway, for now, it is still technically possible to access the classic site permissions page.

For example, to access, quick and dirty, the site permissions page, append "/_layouts/15/user.aspx" to the site URL (i.e. "https://<tenant>.sharepoint.com/sites/<groupname>/_layouts/15/user.aspx").

[#3]

Also, for now, you can still create a classic team site (i.e. not connected to a Group) in the SharePoint Admin Center. A classic team site will have the site permission page accessible as usual.

[#4]

And you can connect later your classic site to a new Office 365 Group

[#5]

MS has committed to maintaining the classic functionality so you can still do what have always done, but when you do this you won't get the integration with a connected Office Group.

When you connect a SPO site to a Office Group, the Office Group members are automatically included in the SPO Members group and the Office Group owners are included in the SPO Owners group. They may not have access to any libraries that have unique perms - this will depend on which SP groups have access to the library, Custom SP groups won't know about the Office Group members. but you can always add the Office Group to the custom SP Group. In a recent migration, we decided that the historical security approach was unnecessarily complex so we left it behind and started over. I recommend that you take a very close look at those custom perms to determine if they are really NEEDED, in many cases they were implemented just because someone thought it was a good idea but there was no real security requirement.

[#6]

Hi, Harmanna.
From what I understand, this largely depends if you plan to use your SharePoint sites with other Office 365 services like Teams, Planner, etc.  

If it is not a factor, you may want to check out SharePoint Migration Tool to preserve custom user permissions. 

Fred