Exactly correct. Power backs into jumbo and power formations, scta backs in spread formations, if I have a twin headed backfield with similar backs they split all the formations etc.
And yes they stick after you reitre the coaches!!! It works beautifully.
When I advance the week you will see in the box scores RB carry distribution based on the team and how may formations I sub in the other guy.
Depends on the teams, scheme and usuage IRL that I base my sub packages on.
For example the 49ers. CMac is the lead workhorse......so for every 10 carries he gets (not including the passing game which is all his) I would life to see at least 2-3 carries for the other guy. So a 80/20- 70/30 split ratio with true workhorse situations.