[adhesive_wombat]

The Dinorwig turbines are (like most hydro plants) Francis turbines. The blade still have an angle. Like a PC case fan, the angle is the same direction whether or not the turbine is "braking" or "pumping". But there very likely are tradeoffs in the turbine design to keep both functions relatively efficient.

There are also what are called ternary sets, which are the generator turbine, the torque converter (a massive clutch) and a pump. A good diagram in here: https://voith.com/corp-en/11_06_Broschuere-Pumped-storage_ei.... These are used at another Welsh pumped storage station: Ffestiniog.

Helical gears (the ones with angled teeth) are used not because one direction is better than the other, but because they have a larger contact area and allow larger forces for a given tooth size (module) and lower vibration because multiple teeth mesh at any time rather than one-by-one. The angle can go either way, and, indeed, can go both ways on one gear (a herringbone gear) to nullify the axial loading.