If you are training or racing in steep terrain, you inevitably will switch between running and power hiking. You will notice a significant power difference between hiking and running. You will notice that if you run up a steep slope it will take a lot of energy, and if your pace drops walking becomes more efficient and will save you energy (hence the rule of thumb in ultra events: if you cannot see the top, walk). As walking is more efficient, power drops when switching to walking.
To be able to use power in steep inclines, you need two targets: one for walking and one for jogging/running. We currently have no test to determine sustainable walking power. At this time, you need to determine your own power hiking target that you can sustain.
If you use RSS to determine training load, consider that RSS gets impacted since it relies on CP.