I wouldn't recommend using either powerlifting or Olympic lifting to improve your cycling. IME using a specific weights program which improves cycling works. Not much else does. If you just want to have fun in the gym and don't care about the cycling, that's another matter.

Be that as it may, with twice a week one gets improvement. With once a week one holds steady. Therefore the usual prescription is 2-3 times a week in the pre-comp period, i.e. winter base, then once a week during comp season.