Division capacity is 10 +1, second mag can only have 10 at every match that I've shot. CDP is 8 +1 by design of the gun and some in ESP may not reach a capacity of 10 and shoot at given mag capacity +1.
To the question at hand - YES - mag at capacity plus a round in the chamber 100%.
Any handgun for protection should always be loaded to maximum, unless loading to the maximum affects the cycling of the firearm, or it is a handgun that it is dangerous to have one in the chamber, like some early revolvers and some semi-autos. I probably wouldn't be carrying the type of handgun listed above in my exemptions for personal defense.
The worst situation I can imagine is being one round of ammo short to save my, or those I might be protecting, lives.
Depends on the pistol. If I top my PT145 off it doesn't want to feed the top round in the mag - so I go with 9+1. Totally reliable that way. My Glock 30 doesn't have a problem with 10+1 - but that last round is real tight going in, and it requires quite a bit of force to insert under a closed slide. So again, 9+1 is the way I go with the Glock. My 1911 is completely reliable with a full 8-round magazine and one up the spout - so that's the way that one gets carried.
My advice before carrying any weapon with a full mag and one in the chamber is to test it that way. Some pistols don't like it, some don't care. To me it comes down to the gun and it's preferences before my own.
Load mag to capacity, then chamber one off the mag. This way if I have to unload for some reason, I dont have an extra bullet rolling around. It's happened a few times when someone wants to see my sidearm (like the girl at Gander Mtn one day thought my 92 was a Beretta and wanted to see the difference), I can unload the mag and chamber then stick the loose round back in the mag. I also unload my pistols when they go back in the safe, but I dont unload the mags. So again to keep the extra from getting lost or having it loose in the safe, I just carry what the mag capacity is. Personal preference......