1. I think (but I’m not positive) there is always a negative impact to informing of redshirt. For a lot of players, it’s enough of an impact to drop you completely. There are some instances, especially if no human battles emerge for the player, where you can inform late in the process, and the player will sign. I suspect this is most effective when you know exactly when the player will sign, ie if you’re a D2 team recruiting a D1 pool player with a first period signing preference, and you know he’ll sign that first cycle of RS2. But I haven’t tried this, so I can’t confirm it always, or ever works.
2. 140 max. And if you start a recruiting session with 10 open scholarships, it scales down from 140, so you sign a guy and you don’t still have 140, you have something stupid like 124. On a related note, you won’t be able to cut any crappy players, unless you sign guys in the first session. Your AD won’t let you cut until you have 7 guys on the roster for next year.
So basically what you want to do is sign 4 guys somewhat late in RS1, or very early in RS2; then when the second period starts, you cut guys as they sign, so you’re maintaining that 140 stockpile as long as possible.