EW only works against SAMs and AAA guns with EW, so optical AAA guns with optical FC aren't affected by a plane or helo's EW value.
Therefore a 12.7 Dushka or a 40mm Bofors firing over optical sights at a "stealth" plane emitting zillions of watts of jamming or flares does not give a hoot, if it is passing by in broad daylight and hence perfectly visible by mk1 eyeball. That is why stealth bombers tend to be painted black and operate when the sun is down (duh
). A shoulder fired SAM or a radar guided gun (FC 100+) will do, whether its night or day.
EW only works against electronics. (Radar AAFC 100+ or AAGW).
An AA gun with normal FC (sub 100) is an optical (or whatever) on-sight system and so is not in the EW battle. Normal visual rules apply there.
Planes with EW ratings less than AAA systems EW are over-matched and wont fare too well. Conversely, if the AAA system is over-matched by the planes EW then they wont do too well vs the planes.
As with all things SP, its an abstraction, and a broad-brush one at that, dealing with a side show to the main meal of land warfare (cloud punching). Note there is absolutely no split on IRCM, ECM, laser CM etc.