I’ve done cottonwood pass to Whitney and variants thereof a few times. It’s easy trail with gentle grades, but how your body performs at altitude can vary. I lose about 35% power (which I can measure because I run and use a heart rate monitor, and I’m about two thirds of my low altitude trail running pace for a given heart rate when I’m above 10k feet).
Camping depends on what you look for in a site. If it’s simply flat ground with space for a tent then you’ll almost never have a problem. If you like to camp next to water then there’s potentially some dry stretches.
On the cottonwood pass route, the following have water and flat ground.
1mile just by the old cabin at the head of the meadows
4.5m chicken spring lake
10 soldier lake (if you go that way)
11 lower rock creek lake
11-15 multiple locations on rock creek
16 guyot creek
20.5 lower Crabtree
22 upper Crabtree
24.5 guitar lake
25.5 tarns after guitar lake, and others over next half mile
28 flat spots at Whitney trail junction if there’s snow for water, if not it’s dry
30 summit similarly only water if there’s snow.
