Biggest thing to worry about is their IP/G due to in-game fatigue. The further you go over their real-life IP/G, the more in-game fatigue will hammer them. I try really had to keep max PC below/around their RL IP/G * 16.
For starting P, it really depends on your rotation size, as a 300-340 IP pitcher will have dramatically different PC in a 3-man rotation compared to a 4-man. I use the following for my PC setting for starters: ((RL IP x 1.1)/# of projected starts) * 15 for TPC and ((RL IP x 1.1)/# of projected starts) * 16 for MPC (so long as this doesn't exceed their IP/G * 16).
For RP, I use ((RL IP x 1.1)/# of projected appearances) * 15 for TPC and ((RL IP x 1.1)/# of projected appearances) * 16 for MPC (so long as this doesn't exceed their IP/G * 16). I typically use 40-65 projected appearances for Long A, 60-90 projected appearances for Setup A and 30-50 projected appearances for Closers (if I use one), but these can vary dramatically depending on IP of the guys I use (for example a setup with 125 IP is going to get more appearances than a setup with 60). I typically don't experience fatigue in any way using this system, and can typically bump pitch counts higher toward the end of the year/playoffs.
Hope it helps.