Payload optimization between SEA and HKG or ICN?

Hi folks —

Does anyone have experience flying between SEA and either HKG or ICN? Wife and I are planning a trip that way in early November.

It’s hard to discern what’s going on with these flights on travelnet. Some of them show departing with negative seats remaining in the cabin.

Travelnet also has lots of warnings about payload optimization. Does anyone have experience with payload optimization? Do they always turn all non-revs away on a payload optimized flight, or would they let a limited number on? Does it depend on your priority? And when Delta says “frequently payload optimized,” does that mean 90% of the time, or 10% of the time?

Thanks!