Ok first question
yes your car is lower than the normal IS250 (only slightly not even visually noiticeable untill you put another IS250 next to yours)
S vs H
S is more for sporty
H is more luxury
S is lower and also harder, but with the S techs you will notice that its got around the same stifness as your sports suspension
so S techs has the vote for me
(i personally had S techs when i coudlnt afford coilovers, it was one of the best mods ever on a 250)