On militarised subsystems, I understand every ship that has it goes towards your combat ship total (not a problem at the start but I guess will be if you want to max your point total with actual fighting ships).
Carriers are a fantastic class of ships and swarms of torpedo bearing fighters are terrifying - ordinarily they bump off shields but if just catch even a capital ship with its shields down or facing the wrong way to really ruin its day. So far, I’m thinking numbers of low tech bombers/heavier torpedos > fewer higher tech fighters/fancy blasters.
Fast frigates can grab one or two of the important objective points in the battle which will, if I am the smaller side, give me a sometimes huge bump in reinforcement points allowing me to bring in more ships immediately. Once these points are spent I can lose the objectives and go into the negative but that’s fine; I usually scramble to bring in an additional cruiser or two which makes all the difference.
edit: one other point is burn speed - keep in mind your entire fleet burns at the speed of your slowest ship. Something to think about before you grab that gigantic slow freighter.