Come on guys let's try to use common definitions.
Over power the the sun could mean a lot of thinks.
I see good examples utilizing both ND approach and HSS approach.
Using HSS means that the lights turn into constant light sources and are not doing to contribute to action stopping. That is now the shutter's job.
As for Eintein, it has no HyperSync or HSS capabilities. At full power it could possibly offer a 1/3 to a little more Hyper Sync. And it does not offer any HSS rapid flashing capability.
ND filters are an aid for using wider apertures at a given shutter speed ISO setting.
Bobby, I'm can't figure out exactly what you want to accomplish. The HSS capable lights offer an option.
ND filters offer an option. I'd be disinclined to use them together.
Personally, I don't want to use ND filters. So, my options are X-Sync and small apertures, which taxes the flash. Or HSS which permits higher shutter speeds and also taxes the flash.
On a shoot I often go back and forth between the two options depending on the situation. That'a one of the benefits of the HSS approach.