You may know this already, but some Asia First services to DPS are actually non-existent, e.g. JL729 is a 744 with only Y and J sold. CX DS - HKG is the same - and the A330s are Y / J, the 747 is Y /J with elites sometimes being accommodated in the F cabin (which is otherwise not used.) You will never find F awards on these flights, as they do not exist on these.

But is an F award worth it on JL or AA, or AA on the transpacs? Personal preference will come into play here. I've used 'em and have not been disappointed, but YMMV. With your flights, I'd probably opt for an all J award an save some miles for the future, or indeed overnight at YVR.