I've posted this many times over the years.
The easiest way, with the best chances of success, is to migrate from a backup drive.
And that will go fastest if your backup is a "cloned" backup created with either CarbonCopyCloner or SuperDuper.
Both are free to download and use for 30 days, so "doing it my way" will cost you nothing.
You want to be careful to do the migration THE VERY FIRST TIME you boot the new Mini -- otherwise, you could end up with multiple accounts and permissions problems.
Quick overview:
a. Just before the new Mini arrives, create your backup (or, if you HAVE a backup already, just run it "one last time")
b. When the new Mini comes, take it out of the box, set it up, and connect the backup BEFORE you press the power on button
c. Now press the power-on button, let it boot, and begin setup
d. At the appropriate moment, setup assistant will ask if you wish to migrate from another drive. YES you do
e. "Point the way" to the backup and give SA time to "digest everything" on it. It will take a little while
f. SA will present you with a list of stuff to migrate (apps, accounts, settings, data)
YOU CAN GO TWO WAYS HERE:
1st:
Just migrate everything. But be aware that some apps may require upgrading, or may have no upgrades available.
2nd:
Migrate everything EXCEPT your apps.
Now (again, you need a cloned backup for this) you can "test" your apps by running them from the backup (your preferences will get migrated with your accounts). My guess is that if they run from the backup, they'll run from the internal drive, so now you can "copy them over manually", reinstall them, etc.
WHAT YOU CHOOSE IS UP TO YOU.
g. With the above choices made, let setup assistant "do its thing" with the migration. Again, it will take a while.
When done, you should see your login screen, just as before.
Good luck.