I can't give you information about specific trails.
My experience is you can hike faster in the Sierras and Rockies. More open space and fewer obstacles unless going off trail. Also navigation is much, much easier for me.
Altitude can affect some people adversely, not only alt sickness but less oxygen to breath. If you are doing big elevation gains especially high up many folks suffer and go really, really slow.
So it is hard to give advice.
In thunder storms get down below tree line and don't be the biggest thing are next to the biggest thing.
Once you get going, it is just walking. Only I like the views better.