Ill share my best planet taking tricks, (I didn't invent them and I do not own the copyright on any of them, and this is for purely non economic purposes).
send in one scout for the ai to chase (use shift key to stack move orders orbiting the outer edge of the grav well), to handle even the tough planets. Send in one scout first, the ai well attack it if no other ships arrive first, jump a small fleet in and kill the ai well they chase the scout, they well let themselvs die, they mostly not brake off unless you send in a colony ship ( ya can still use colo cap), the planet bombers well break off if you take the planet, the javs well brake to attack light frigs and the flack well stop to chase fighters, but this strategy can be used take planets with as few as 5- 10 scout ships (nothing well attack them and they have +100% damage vs the planet bombers and javs), use the fighting scouts to kill P. bombers and javs, take the planet, build 1-3 turrets in a cluster to kill remaining defender ships then just take your fleet and repeat with the next planet. try it a few times to work it out for yourself.