Are you looking for a photo, video or a bit of both camera?
Definitely skip the A7 II for the A7 III if only to avoid the dreadful NP-FW50 battery.
Be aware the F-to-E adapters are not in the same league as those for EF-to-E. Canon are much more obliging than Nikon when it comes to releasing details of the lens mount and everything for Nikon has to be reverse-engineered.
From what I've read elsewhere, the Metabones adapter is the only one that's worthwhile. Your lenses may well work but AF won't be speedy. Probably better with the A7 III than II.
As an A7r III owner, it pains me to say it but your needs might be better suited to the Z6.