Thank you all for your advice.

I will be flying from Ottawa (YOW) and, the flight is in the late morning. So I would be clearing immigration/customs on the Canadian side.

From what I learned from this thread,

1. I should be able to access the lounge on arrival as long as the lounge is not full.
2. I most likely will have to exit from the airside, go to the Alaska Air terminal, and go thru TSA to get to the Alaska gate.
3. I also have TSA pre-check, so heading to the Alaska terminal one hour prior to departure should be enough? or I should assign more time to do so?

Thanks again for your help and knowledge,