If both devices are running the same macOS as was the case with my 2015 13" MBP to 2021 14" M1 MBP you can do a wireless transfer using Migration Assistant.
Of course it's still a very good idea to have a backup, eg Time Machine or clone but I was impressed at how easy this process was.
Here are Apple's instructions;
Transfer to a new Mac with Migration Assistant
There is just one pitfall in the process.
Obviously you need to perform an initial setup on the new device prior to this process, just to access Migration Assistant if nothing else.
Ensure that you recreate exactly the same user name and password on the new machine as your have on the old one
if you intend the new machine to replace the old machine. This was my intention so that was what I did.
Now when you get to "On your new Mac; Step 2" you must choose "Replace" it seems a bit odd and confusing but if you don't do this ie. choose "Rename" instead, you will end up with two identical user accounts, one empty and the other with all your data from the older device.
So, although you have already created a duplicate user account with the same user name and admin password you must choose "Replace" with the one from the old machine.
Anyway, that's what I did, and the result, which takes a while (I let it run o/night) is a complete duplicate of the old device on the new one.
In the morning I shut down the old MBP and began using the new M1. At a later date I erased the old MBP and repurposed it.
