Capacity & no free lunch
I enjoy these woods pistol posts, having spent a good bit of time afield, on the job and off.
I think you are asking to much of a handgun to serve as a both "wilderness gun" against bear and cats AND as CCW piece which you can conceal and go about daily. (FWIW, I have zero experience w/ cougar, but I have worked and been around black bears a good bit at other parks, but not here in AL). One type of pistol serves the backcountry role, another the CCW role.
I have not looked up any tables but suspect a short bbl 10mm becomes essentially a .40 S&W, which I do not see as a bear or cat pistol. We accept certain calibers (such as .40) for CCW because we must conceal them. I don't see the need for that in a woods pistol. Portability is important (who wants to carry a pistol gripped 12 ga pump around the backcountry constantly) but not paramount. Plus I suspect that a short 10mm becomes a flamethrower and a handful to shoot well. The full size G20 is packable, controllable and gives the advantage of full power from the 10mm ctg.
The G20 offers high mag capacity as well. Probably won't need it, but it's nice to know it's there.
It won't conceal easily though, in moderate or warm climates. For that you need a smaller pistol.
Finally, I think a greater threat exits from human predators than black bears. I have done some incredibly brazen (and stupid) things with black bears. I am aware of one fatality here in the SE that involved a pair of black bears and an adult woman. (some day I will FOIA the reports) In my two dozen plus trail contacts, (the bulk in SHEN, VA, ) most split, very quickly. Interestingly, last fall I went to GRSM NP w/ the family. We saw 3 on the trail, all very conditioned and not fearful of man at all. (We saw at total of 8, 5 more from the car) .
Your cougar stalking account is chilling, and demonstrates knowledge aforehand and intent. One more reason to stay armed w/ that type of threat about.