You're comfortable with the Glock...keep it. Also..KISS.
Don't overload with all the extras. Extra magazines, fancy holsters, and "trick" ammo are of no real use.
Cougars are small animals, most around 150-180 pounds...about the size of a two-legged predator. The primary difference between a BUG and the cat is their attitude. A BUG will change their mind as soon as you give resistance. Unless on drugs(alcohol included) to alter perception, when the noise starts, there are better places to be...especially if there is blood already involved. Practice 'til you auto-matically make 'em bleed.
Many cat hunters-guides use a .22 or .22Mag and have no problem dropping cats. I'm not saying USE a .22, I'm saying that a 10mm OR .45 will be more than plenty. If you have to use it, don't shoot then observe...keep shooting until the situation is over, one way or the other.
Just practice 'til YOU know you're good with your chosen equipment.
A .45 doesn't NEED +P, it is effective because it makes a BIG hole. Don't worry, it breaks bones, and the target leaks! Use +P if it makes you feel better, but all it does is increase wear on the gun. Practice with what you'll use.
The main "claim to fame" of the 10mm is deep penetration. It breaks bones just fine, and the looong holes, with probably complete penetration, bleed well, too. Kinetic energy, in and of itself doesn't mean much, but destruction of important parts, and loss of blood, do.
Practice putting holes in important places, rapidly. Oh, yeah...practice starting like you'll be when you get into the scenario. If you wear a long-sleeve shirt with a large backpack, practice that way. If you wear a small "day pack" and shorts, practice that way!
Remember, a "double tap" is NOT what you want...you want two aimed shots fired quickly.(two or MORE)
Handloading? IF you want to, and have enough space, and time...by all means do so, but the money spent on equipment could be spent on ammo for practice. It would appear by going to websites that cater to reloaders, that EVERYBODY reloads, and it's really cheap. Not so. It can be a royal pain, because there are a LOT of things you can, and can't, do. You will have to learn what.
That being said, I've been reloading since I was 12 years old! I'm 62!
When I started, I told my mom that I'd be saving money. HA!
I used to load so I could shoot...now I shoot so I can reload. It's become a sport in itself.
Oh, yeah...Did I mention practice??? In a situation, you will react as you are trained, so train as you want to act.