It's always going to vary a little with drones, turning towards / away from different light etc.
Really, for video especially (rather than long shutter photos), a good guess becomes easier as you trial ND filters.
For video, blue hour I just leave an MC-UV on.
Use an ND 4 or 8 on the verges, golden hour or slightly lighter.
Between that and mid morning and same mid afternoon to sun still a little above the horizon, I find the ND16 is good.
Middle of the day ND32, haven't used my ND64 much at all, but might be handy one day for white sand beaches or snow.
For slow shutters, unless you have a variable aperture camera drone, you will probably need much stronger ND filters to do anything like smooth water shots.
Tried my ND64 on a tidal movement once, very marginal effect (that was an M1P).
I'd estimate 8 to 20 stops would be required to make a decent difference, and then I have to keep the drone very still.
I have a NISI app that does the estimates like you posted above, and I did have one PolarPro does too, was interesting to play around with inputs and see what filters they recommended.
It was more for traditional camera though I feel.
Cheers.