Cardio events = front carries, tire flip, drags, truck pull, etc....
Maxing events = axle dl, heavy stones, overhead press series, super yoke, etc....
I would alternate heavy and light weeks and by exercise as well. For example:
Week 1
heavy back (max reps or weight)
light overhead/bench
heavy legs (max reps or weight, whichever you didn't do on back day)
Week 2
light back (speed)
heavy upper body (max weight or reps)
light legs (speed)
If you work out a fourth day I would say to use it as a GPP day.