power shrugs instead of rows for example. farmers walk at the end instead of
some of the other stuff listed. I dont know side DLs but if it is a mere abs
exercise then you can do them at the end of the workout.
IMO, power shrugs aren't really an appropriate alternative to rows. Just do them at the end of one of the workouts as an assistance lift, and as long as you don't go nuts on them your other lifts shouldn't suffer. Ab and grip/GPP work would be fine at the end of regular workouts or on off days.
I feel that you can add anything you want to the 5x5, as long as you stick to the core exercises(bench/squat/DL/Row). Just don't over do it with too many exercises. If you do powershrugs, then maybe sub it in place of your normal shoulder exercise etc..
I do shrugs once a week with my 5x5. Don't replace the core workouts, just add some non-taxing things at the end. Shrugs, any abb work etc don't burn alot of energy so they are fine to do.
I do abs almost every day, you can do abs all the time. As far as I can tell, they don't fatigue you one bit unless you are doing some hardcore workout. I do shrugs probably once a week, lower back hypers once a week.