Any half decent levelling compound nowadays should have a cured strength of around 30Newtons which is basically like a road. You can set anything you like on top of them once they're cured, so don't worry about your sanitary ware, definitely level the floor first.
It does not matter how long you leave the leveller once cured before installing a floor covering, in fact the longer the better.
In regards to cushion floor vinyl, install your sanitary ware first. Do not set these on the cushion floor!
I take it you intend to have the cushion floor professionally fitted, as a DIYer won't have the skill level to cut this in around toilets and sink pedastils etc. It may also work out cheaper for you to have your floor layer to level the floor for you when you factor in the cost of a spiked roller etc. Hope this is of help