Hi J,
Glide and grip is all about having the proper ski for the proper
person.

Say you weigh 100lbs. Your ski be it wider or not is flat under your
foot(grip zone)
at 120lbs the skis are no good for you as it would take 120% of your
total weight yust to get grip.The ideal ski for a person with 100lbs
weight is one that is flat at 75lbs. This is because on every step you
have to flatten the ski to get grip.
Sure a lightweight person could get more skibase in the snow if they
get a wider ski.
This has nothing to do with glide or grip. A wider ski does not glide
faster or grip better if the skis have not been selected properly.
The optimum is to have your skis selected by a competent ski shop.
RW