If I had to choose one exercise for chest, I would say Guillotine press, and second Dumbell incline press.
Those two exercises and BANG!
Really I would say the last thing you need is decline presses.
Most chest exercises hit pretty hard the lower chest. And even more the mid chest.
For example flat flys, hit way more lower than upper chest.
So do flat presses.
I would say to you: focus your training on the uppper chest, so neglected and at the same time, not easy at all to hit really well, as the “mid” portion and lower at least in comparisson.
So in conclusion
Flat exercises hit more lower chest than upper.
So why doing decline exercises to even potentiate more this imbalance.
Man I tell you this, when you have a good upper chest, it really does make a difference in the way your chest look.