Faster (wave 1) runners will typically go with a single layer and one or two may have wind jacket with a pair of gloves and a lightweight cap tucked into the jacket pockets if the predicted temps will be below 30 at the top or they are predicting high winds.
Slower (wave 2) runners should bring a pack with gloves, hat, jacket, extra shirt, food, water, pants, etc.
The faster folks assume that they will be able to get to the top before trouble (mid-day storms) show up. Slower folks should assume that trouble will get to the top first and that it is best to be prepared for it.
There are some slower folks who try and emulate the faster folks thinking that it will make them faster (like not bringing water). They are easy to spot, they will typically have two SAR team members on either side of them above tree line.