Bought a new NAS with bigger drives. Easiest/fastest way to migrate?

Hi everyone, after nearly eight years, I have finally decided to upgrade my DS916+ to a DS923+. There was the leak that the 925+ is coming, so I am still weighing returning the 923+ I bought last week. That being said, I am a little concerned about the best method for migrating everything over from my old NAS to the new one. The 916+ unfortunately is ext4 while the new one will be brtfs, at least that is what I think would be the best option.

If I kept the new one as ext4, I believe I could just do a straight migration using the migration assistant, and be off to the races, is that correct?

Using Hyper Backup, it appears I need to have twice the capacity as my old NAS, which I do have, but it looks like I have to back it up, and then restore it, which seems like twice the work.

Of course, there is also just copying/pasting from one NAS to the other via a host machine using something like TeraCopy with the option to have it verify each file.

Is there another method I'm missing here? My end goal is to just transfer all the old data to the new data with the least risk but also least amount of time involved to complete. Thanks in advance.

*EDIT* Thank you everyone for the suggestions. The 923+ is already on its way back to Amazon, and whenever the 925+ is in my hands I think I will just do a simple rsync or mount the old NAS on the new NAS and transfer it that way.