Yes, your fit changes as you get fitter. I've had my current road bike for about six years. When I bought it I had to install a shorter stem because I wasn't comfortable being stretched out in the drops. But after a while I was able to reinstall the original stem - I was a bit lighter, and time and repeated practice had made me a bit more flexible than I'd been before returning to cycling.
You can certainly go faster in the drops. Typically, if I move from the hoods to the drops my cadence (and therefore speed) will rise between 5% and 10% for the same level of effort.
If you want to experiment, all you do is remove the stem from the steerer, take out a spacer or two, replace and tighten the stem wI the removed spacer(s) above the stem instead of below it. It needs care, because when putting the stem back on you have to ensure that the headset is properly tensioned - too tight and you can't steer properly, too loose and you have play in the headset which isn't safe. It's easy to do, but slightly difficult to describe. I'll look for a video for you.