A double stack sub compact will fit large hands just fine, even offering a 3 fingered grip with extensions or full sized magazines. Even a longer barrel can be dropped into many of them. I have moderate hands and have trouble putting a good grip on a G29 frame, but I can still manage. Think about the versatility of a G29 or 30. 10mm or .45, little or big, long barrel or short barrel. It's a gun you can pocket carry, or even load up to defend yourself against bears. No loss of power needed, just as much as ever with plenty of concealability.
As to hitting what you aim at, if you think that as a concealed carrier you are likely to need to use your sights, or that you are likely to have to shoot beyond 15 feet to protect yourself, you are almost certainly mistaken. Within the vast majority of SD situations, hip firing and fast paced point shooting are what you're looking at. Either that or a lot of trying to get a sight picture you're not likely to get well on a fast moving target. A 2.5"-3.8" barrel will accomplish this just about as well as anything else, with the only problem being a variably lowered velocity. If you'd like, you can even get a laser.
If you have any friends who can let you try a smaller gun, just try gripping it really tight with one hand, pointing it like your finger at a target 10 or 15 feet away, and squeezing the trigger as fast as you can. You should notice a very tight grouping.
As to capacity, I don't know how much you value your life, but for me, I want more ammo on me, ready to go than I can possibly use. I also want to be able to shoot lethal assailants until either they drop to the ground and stop moving or I do, with little likely need for reloading. As the sayings go "when in doubt, empty the magazine" and "don't stop shooting until you see brains".