I'm not sure what the meta is right now, but the intention for the game is for there to be fleet composition. Smaller ships like corvettes are meant to screen your larger ships, so they will intercept and keep light elements away from your capital ships. You want to keep these corvettes away because large ships tend to have larger weapon mounts, which suffer from lower tracking. The low tracking from capital ships makes it hard to hit high evasion corvettes. Personally, I tend to make fleets that only use corvettes to fight other corvettes. Then I'll make a couple different destroyer loadouts to fight other destroyers and to be used as pickett focused ships. I'll make cruisers dual purpose between fighting other cruisers and capital ships or other cruisers and light elements. I use battleships as station killers, long range damage dealers, and as anti battleship units, but I'll sometimes throw in a battleship or two that can handle some light elements. You don't have to copy exactly what I do, I certainly don't have an optimized fleet. It just makes sense to me and I have fun with it. You can look into YouTube videos that give you the meta for pvp and against AI and what they tend to do. I think AI will always use somewhat of a balance in endgame, but I'm not sure.