There's no right answer, but here are a couple of thoughts:
Some folks have hacked the Lightroom Importer so that you can go directly from Photos to LR - it may involve renaming the library, but worth googling.
The difference is size:
This is down to the nature if Jpeg as a format. It's not actually an image format, it's a compression format. When you view a jpeg what happens is the file is decompressed, showing you the image within. Photos, when it exports, is not exporting your jpeg, unless you export the original. it's exporting your photograph and putting it into a new jpeg, and the size depends on the amount of compression applied. That's why you get files larger than you imported - Photos is using less compression than your camera.
There is no way for you to maintain the link between your original and your edited photo in this migration.
You can export both and import both to LR, but then you have a lot of duplicates.
You can just move your edited versions - but then you don't have the original files and you can't revert
You can just move your originals and start over with your editing again.
Those really are your options, and this problem arises whenever you migrate between these kinds of apps - Photos to LR or LR to CaptureOne, or CaptureOne to OnOne Photo Raw and so on. They each use their own methods and algorithms to manage the relationship between the master and the version.
FWIW - when I migrated I exported the originals of all my Raws but the edits of all snap shots. Still found myself reprocessing 20+k raws...
As for the printing question: a rule of thumb suggests that the bigger file size mean more data to print, but there are other factors - the sharpness of the image, the quality of the printer and so on - that have much more impact on the output. Trial and error is the only way I can suggest.
