Q: migration assistant or just drag and drop user directory

I personally prefer the drag-and-drop method myself as it gives complete control of those files migrated and therefore does not move "baggage" to the new and clean OS.  Obviously this is only something you should do if you understand what should an should not be transferred.

I always complete the new OS clean install, then update Mac OS, then create my user accounts in the same order, then log in and out of each, then use drag-and-drop from a Target Disk Mode from my old drive or a clone to get things in place prior to launching any applications.

I'd recommend only using drag-and-drop on the "contents" on important user folders.  So, when copying, select the contents of your old "Documents" and drag it to the established "Documents" of the new account for example.  Replacing such directories created as part of the user account will almost certainly introduce both POSIX and ACL permissions issues but copying contents does not as long as your user accounts are the same and were created with the same UID.

Be particularly careful with your ~/Library/.  Copying select files and folders from ~/Library, ~/Library/Application Support, ~/Library/Group Containers, ~/Library/Preferences, etc. can go along way in not needing to set up all of your applications and licensing again.  Just be very selective and when in doubt, leave it out at first and then come back and get it later if you feel that you are missing something.

As a result, you have a Mac that runs like new, without any baggage from old installs and applications, but doesn't require quite as much setup as a clean install would.

After re-reading the title of your post, I just want to make it clear that you should NOT just drag-and-drop the entire "/Users" directory, nor should you drag-and-drop an entire users user profile (i.e. home directory).  Instead, I've found that it does work well to drag-an-drop the contents of specific files after allow those users to login and out of the new mac to create the initial home directory structure for each account (which gets the permissions right for the user).