"Moving up" from a 15" form factor, the 2019-design 16" MBP is the natural choice.
As mentioned above, you can use either CarbonCopyCloner or SuperDuper to create "a clone" of your internal drive that is mountable "in the finder" like any other drive.
Then, you can connect it to the NEW MBP, and "manually copy" the things you wish to bring over.
Both CCC and SD are FREE to use for 30 days, so using either to create the clone will "cost you nothing".
IF the only serious problem you're having with the 2012 is with the battery, you might consider using "setup assistant" with the new MBP. It will bring over 3rd-party apps, home folders, settings, etc., but leaves "the old OS" behind. It works quite well, but you have to "use it at the right time" (very first thing to do is to connect the backup BEFORE you press the power-on button for the first time).
If you go the "manual migration" route, be aware of two things you need to do regarding a cloned backup:
1. You need to mount the drive on the desktop, bring up "get info" (on the entire drive), and then put a checkmark into "ignore ownership on this volume" in sharing and permissions -- remember to click the lock first.
Doing this will avoid any "permissions problems" that can happen when moving from an old account to a new one (the Mac will still see these as "different" accounts and give you problems otherwise).
2. You must be careful about WHICH FOLDERS you try to copy from your old account into your new one.
You CANNOT COPY "the top level" folders in your account -- the ones named "documents", "movies", "music", "pictures", etc. In the old days, these were "more than" folders, they were "symbolic links". Not sure if that still applies now.
However... you CAN COPY files and folders that are INSIDE OF these top level folders. That would include things like the iPhoto library, individual files, etc.
Take these two issues into account, and the manual migration should go smoothly.
I also suggest you keep some HANDWRITTEN NOTES as you go along.
Well, at least that's necessary for old guys like me...
