2) The campsite I was able to reserve at Whitney Portal appears as though it might be quite a hike from the Trailhead. Is it possible (as well as advisable) to swap this for one of the Walk up Backpacker sites that are closer to the Trailhead?
Just hoping to tap some of the experience/expertise on this site.
Some of the reserved campsites are a bit down the road. So if you're staying there, the morning of your entry you'll have to pack up and drive up and park near the trailhead. This parking lot is the same place you'd be parking if you stayed at the walkup sites.
So you're not saving any distance.
Also, even if the reserve sites are farther away, THEY'RE RESERVED! The walkup sites are not. Big difference between knowing you have a site for the night, and hoping you have a site for the night.