An inhibit doesn't set the intensity level it limits what the maximum intensity can be so you can still have playbacks that set something less than 100% and they will still work as expected.
e.g. You create two playbacks one of them (a) sets a fixture to 50%, the other (b) sets another fixture to 100% then you create an inhibit playback (i) with both fixtures at 100% (it doesn't have to be 100% but it usually is).
With (i) at full, (a) and (b) work normally - 50% and 100%.
With (i) at 50%, (a) will be at 25% and (b) at 50%
With (i) at 0%, both (a) and (b) will be at 0%
One thing to notice is that after you have created (i) you need to take it to 100% once to make it effective - if you just leave it at 0% it doesn't inhibit at all. A spin off of this is that, if the fader isn't quite making it to 100% (because it needs cleaning for example) you can never make it work.
I generally find it is easier to delete and re-create inhibits than to try updating them if you need to add or remove fixtures.
It's quite a powerful option but you have to get your head around it.
Incidentally, there's also parking but I'm not sure if you can do that on S series.
Or you could change the fixture defaults, this would put the ambients on unless you had a playback to set them off but the GM or an inhibit that included them would still put them out.