I'll offer "my way".
Follow these instructions, and I guarantee a success rate of 99%.
First, you'll need an external drive large enough to hold the contents of your friend's old Mac.
You'll need CarbonCopyCloner. It's free to download and use for 30 days, so this will cost you nothing.
What to do next:
- get the new Mac ready, but DO NOT press the power on button yet.
- put CCC on the old Mac Studio and connect the external drive
- use CCC to clone the contents of the Studio to the external drive
Then...
- take the drive to the new Mini and connect it.
- NOW press the power on button
- begin setup. When setup assistant asks if you wish to migrate from another drive, YES, you do.
- "point the way" to the external drive and give SA some time to "digest" everything.
Now...
- setup assistant will present you with a list of stuff that can be migrated:
applications
accounts
data
settings
I suggest you migrate everything.
- let SA do its job. It will take a while.
- when done, your friend should be able to log into his account, just as before. So... do this and "take a look around" to see if things are where they should be.
Good luck.