To actually sex the plant, your light does not matter. The plant will preflower in veg if left long enough or flower once put into bloom and is sexually mature. The HPS light is useful for bud production and I believe more specifically, resin production. But for sexing, light spectrum matters not.
There will be varying opinions about soil and hydro.
IMO, hydro if done right gives you a greater potential to maximize your plant and it's potential.
Soil is easier... harder to screw up and much less forgiving.
The size of your lights will not stress your plants. The more light better, especially when in flower. What stresses the plant is the heat from lights being to close or the temps being to high from improper venting for a perhaps oversized light. Pick what fits your grow best and tinker. If you can vent and cool a 1000w HPS, run that bad boy.
Good luck and good smoke
