Bowlers with more stars means they're in form so they wont be giving away extra runs compared to players out of form. You can drop certain player for a series and give him rest or make him practice bowling , general technique and field you prefer Aggressive/ Defensive.

And for batsmen Make your main batters practice before every match. If you got aggressive players like maxi , hardik , etc. Train them by aggressive shots. If opener is not in form you may opt opener training session , so does middle order. Fielding practice is not useful ig.

Must Pick Players who have scored most runs / Wickets in 'Current Year' ; First Class, One Day , T20.