My front Spax are set up with 95mm between the centre of the bolt hole and the upper surface of the spring seat. This gives me a ride height around 5mm lower than stock. Obviously, when fitted they can be tweaked if necessary so that you end up with an even ride height side to side. Another approach is to adjust so that the steering arms are horizontal.

Regarding firmness: Start off with 10 clicks from softest and go from there.

Can't help you with the rears because I don't have them fitted!