I've tried both light mix and all mix, both will do fine. Light mix will need feeding sooner though. As for watering, anything between 6.0 to 7.0 will do
You want to water at a pH of 6.5 in soil. And any light mix with a good amount of perlite for good air flow will work. Just water them lightly to avoid suffocating the roots and they will be happy. Good luck!
The ph ~6.5 but if it is at 7 or 7.5 it is not a problem because you grow with soil. (Soil buffering)
And for the type of soil i recommend a light mix. You will never burn your seedlings with light mix😛