Moving from iMac to Mac mini

Hi everybody,

I'm moving from a Late 2015 iMac running Mojave to a new Mac Mini.

I know the new machine's OS will not take 32 bit apps, but I've got nothing I'm not prepared to lose.

My main issue is to make the transfer safely and efficiently, but not sure how.

As I am, I'm thinking to make a backup, transfer the backup file to an external HDD and then copy it to the Mac Mini and restore that file on the new machine.

I'm sure someone's about to call me an idiot! Please feel free..... as long as you can point me towards the correct method either by advice or web link to instructions!

The only other query I have is that on the iMac, my photos app seems to have a little bug. I can take a photo and import to Photos and then edit it in Preview, but when I revisit the photo and try to edit it again, it just gives a messages saying "Image XXXX.jpeg is empty.

I've had various suggestions from kind people here, but so far nothing has worked. I'm happy to let this issue wait for another time, but I wondered if anyone can say if I'm transferring that issue to Photos on the new machine?

However the transfer issue is the big one for me right now.

Many thanks in advance,

best wishes to all,

Jim