If you think that is a bad idea (or not necessary) then I will do without - and use the default MACs of that device.
It's not a matter of what a random forum user
thinks (you know neither of us three who have responded, do you), it's a matter of what Mikrotik says in the manual: "can be re-applied on the same or a different device (
with the same model name/number)". I guess the wording could be better (like "on the same device or on another device of the same model name/number"), but the message is clear.
Will a factory reset restore MAC addresses? Or is there any other way how to restore ALL MAC addresses on the device (preferably in one go)?
It may, but as @holvoetn wrote, a netinstall is a better option because cleaning up after a restore of a backup taken on another device model is not a typical task so
/system reset-configuration may not remove 100 % of the wrong bits. But these
are just random forum user opinions, as Mikrotik doesn't give any instruction for this scenario they have never anticipated. So maybe
/system reset-configuration is actually enough.
As for changing the MAC addresses to be the same like on the old device - nothing is wrong about that per se if you have your reasons to do so. You can edit the .rsc file created by
/export before running it on the target router and add the mac-address=xx:xx:xx:xx:xx:xx items to the
/interface ethernet set ... commands to have it all done in one go. But as @anav has pointed out, even an export from the very same ROS version may fail to import completely. The configuration export is a regular script, and execution of scripts stops at first error. And sometimes the order of items in the export is wrong so a row of the script refers to an object that has not been created yet. That's why importing it manually row by row, or at least section by section, is a better approach.