I have 4 alts all doing Squads. This is what I discerned from chemistry so far
Mission affinities will increase the % chance of your squad members getting the listed result.
The most favorable chemistry at the start is a % increase to chemistry accusation rate.
This will allow you to learn more chemistry’s on the other squad member quickly.
I have been using this to get as many as I can. But they are very random in the beginning.
Starting at the level 40 quest you start to receive better chemistry result like for Materia.
The % is determined by the preceding condition and the Value of the bonus.
So if it is accompany a Specific class the percentage is 50% better than if "accompanying any other class"
Being a party effect cause it to ½ the % like EXP earned by all squadron members increased by 5%
I think chemistry learn rates increase with the mission difficulty, I get more learned the higher the difficulty, 40 Missions with a +40% to chemistry have about an 80% chance at learning a chemistry