Gynecomastia (bitch tit- gym slang) is something that usually requires surgery, though if starting early enough it could be treated with drugs. Fairly common among older men and young boys before reaching puberty. Different degrees, small around the male nipple to looking like a young girls breast. If over weight, than losing weight (body fat) might improve the overall appearance, but not going to get rid of it..
Doing flat, inclines or declines are not going to worsen it or improve the condition it's...it's just what it is. Some Pro BB'ers have very obvious bitch tits, even in top condition. That's from the abusing of combo's of different drugs for years and throwing their male hormone (and other natural body chemicals) balance way off.
You might be one of the lucky ones who gets good results in that upper pec area naturally, most guys don't. Incline, flat and declines, by themselves, pretty much hit the whole of the chest area, but each can allow a better focus on certain parts of the chest.
Dip's, which can be a much better movement for the lower pec area, because you are pushing down and along side the body, are excellent for lower portions of the pecs. So might suggest avoiding dips and declines presses for a while if worried about bitch tit. With either exercise, not adding bulk/muscle to the lower pecs can be an excellent idea. Just make that bitch tit much more of a notice.
Pec deck fly's are also good for the upper to mid portions of the chest. Would suggest a pec deck where the elbows are resting on pads, rather then the pec decks where the arms are extended way out and gripped with the hand. Much improved leverage on the pecs, with the elbows leading the exercise.
Good Luck.