Well once you have to gain too much bodyweight and train too much to gain the strength, which then interfers with your goals then your strong enough
Power benefits from pure strength gains stop helping after you reach a point where you can't generate the force in the time needed in the activity.
With sprinting, strength only helps at the start and to stop your legs and hips collaspsing each foot strike and absorbing force, plus basic form. After that you only have 0.1 of second to exert force each foot strike, so can see getting stronger after a point in time won't help you to run faster, since you can't use all your strength in that short period of time. It takes about 0.5 sec to generate max force. So you will be just wasting time and resources gaining more strength.
Most people will usually stop benefiting from pure leg strength when they reach double bodyweight on the squat, since by then you bodyweight will represent about 33% of your strength levels.
then you start to concentrate on other things like reactivity and rate of force developement. Ability to fire and relax quickly helps running greatly too, which heavy weight training tends to interfere with
so I would aim for 2xBW on squat, 2 to 2.5x on dead, and 1.25 to 1.5 on bench is enough. Off course this depends on your leverages.
Assuming your doing all of em raw, and a moderate stance fullsquat, strict flat back deadlift and a shoulder width grip bench
There is no reason why you can't train power and strength concurrently. Each will help the other