There are three factors that correlate to the reward you earn: Experience Level, Force Points Earned, and Task Force maximum Capacity. Here are the relations.
1.) The greater your experience level, the greater the reward if Task Force Size and Force Points made remain constant.
2.) The more Force Points the Task Force earns, the greater the reward if Experience Level and Task Force Size remains constant.
3.) The smaller the Task Force Capacity, the greater the reward if Experience Level and Force Points earned remain constant.
The amount of Intel you gather does not correlate to the reward. Still, I do not know the effect ratio between Task Force size limits when other factors remain constant, so I am unable to answer your second question. Sorry. :(