Hi there, I?m also pretty new to the game, but will give my opinion anyway
what I usualy do re. active sensors:
I will give any warship actives with at least 2 to 3 times the range of its weapons (for Non-Missile-designs) as backup.
Then I will have one or two fleet scouts (perhaps paired with an escort or two) with actives with twice the range of my longest range missile on the theory, that it can stay completely out of enemy weapon range while lighting up targets for my warships. That way, they won?t have to go active and give themself away.
Of course, this means my ships are not intendet to work alone, but, IMO, warships should always work in squadrons anyway.
There are exceptions, Escorts designed for convoy duty, for example, will have long range actives, but the regular line units can get away with that, I think.
Re. shields:
I never realized shields would give ships away, but now that I think about it, it makes sense. I will still mount at least some shields on any warship, simply to have some defense against Mesons, which, as I understand it, can bypass armor.
I have a question re. Mesons too: I noticed in the last combat I had, that Mesons don?t seem to hurt shields and don?t seem to do critical damage once the shields are down
(I get messages like: Ship XXX hit by Meson beams for 7 damage) but there was no info to the damage dealt, I get for other weapons, like "Parson NP Turbine destroyed after receiving 2 points of damage"