For "efficiency", you should stick to a maximum of 2 types of aircraft. Perferably in a 5/3 or 6/2 setup. where the larger dictates your primary objective.

For cv6 I think 2scouts 3 ftrs 3 tbs or db is best. For Pcv 2 scouts 2 ftrs 4 tbs or dbs. Use scouts for vesion and mines, ftrs to blind the enemy and escort bombers. Mines and TBs is a nice 1 2 punch, I just think TBs are more fun than dbs I guess.  But I think you have to have some attack abilities or your at the mercy of your bbs to play well. And useing ftrs to scout sucks, they just don't have enough fuel to do the job, turns you into a human macro trying to keep replaceing planes, ties you down.

for me, the best CV is a RF or RA or RB.

RF: 1 scout 7 fighter ( with the scout 5, you just need to be in the good place and you'll make light without difficulty and you can make Fc )

RB: 1 scout 7 DB or 2 scouts 6 DB

RA same for RB.

2S 6F for US.

if you feel like being a complete detriment to your team run 2S 6 TB or 6 DB

always run 2 S though for the mines