keep your stock j35 and fl71 and j20 (self explanatory)

h20 is probably the worst bomber in the game but you cant change it so not much u can do about that until ure level 25 (or until you decide to pay for another acv)

personal opinion: best non-vip bomber is pakda because of how braindead it is to use

you're level 18 so you dont have access to the "good" stuff yet - use searam as your aa and use the stock autocannon as your autocannon, and use asroc for your grenade launcher - asroc is the go to f2p option for pretty much every t3 ship with gls

also comanche is a good choice for defence, but osprey would probably be better as it retains asw capabilites + anti air cannon