Each battlegroup is composed of a single lead ship, a group of escorts, and a bunch of pickets (i.e fleetships). The points are spread evenly across the three though it almost always has some left over from the pickets because it's restricted to low-cost ships for that part and it can only have a hundred or so of them. So those extra points get recycled into the escorts. The escorts can start off being low-mark guardians and whatnot and wind up being high-mark spirecraft and even golems in very serious cases. But generally if the lead ship is a golem the escorts won't be able to be golems because the escort points are split across a minimum of 6 or so ships.
But multiple battlegroups can start from the same point and some may even have the same objective, and will wind up travelling roughly together, so you can sometimes see what looks like a big group with multiple leads.
So yea, if you're seeing golems in those, kill all the golems and that'll probably be all the lead ships
But when it says "X large ships approaching (N firepower)" it doesn't necessarily mean that there are X separate battlegroups. And it never means that any one of those battlegroups has multiple lead ships. It just means that there are that many ships with an internal firepower rating over a certain threshold. Once you start getting spirecraft as escorts, that number can go up a lot.
And yes, a warp jammer command station just removes that specific planet from consideration as a warp target. If you're playing with Cross-Planet-Waves on (lobby option) the warp jammer doesn't matter at all. And it certainly doesn't apply to any other sort of attack.
