I heard that certain types of torts (or even the same kind of tort but more than one male to a pack) will fight and be stressed out. Is this true? Does this mean I can only have females in Titan's enclosure if I plan to get another tortoise?
That's how it is generally, but it's not the rule. Generally you should have at least 2 females per male in the enclosure. But some males can be perfectly fine together. My Russians are 3 males and five females and the males are great together, it's the females that are pushy!!!
It's very hard to find males that will get along together. Even in with a group of females a male can be to aggressive.
The 3 male Russians I just got, from Anja, had to be seperated as they started fighting with each other.
Even female groups you can have trouble with females getting aggressive with each other.
If at all possible the best thing is to have most tortoises seperate from each other.
Danny
what do they look like when they fight? i know that is a silly question, but just so if i do get another and i try to see if they can play nice together first, what are the differences between playing and fighting?
They were fighting Danny? They have been together for the last 3 years (he thought he had 1.3) from the guy I got them from, actually all 4 males were, including the one that went to Kelly. I never saw any fighting between them. lol
Tortoises don't play with each other Kat.

They open their mouths and try to bite each other. When it's 2 males they face off and try to bite each others heads until one gives up and turns tail. Then the victor will bite legs, tail and shell of the loser. They usually draw blood.
Number 3 and number 2 were going at it Anja. Mouths open trying to bite each other. Number 2 got a nice cut on top of his eye before I seperated all 3 of them. They must be feeling their oats here.
Danny
Every situation is a bit different. You just have to give it a try and see if it works for you. Just always be prepared to have to separate. Sometimes aggression or stress will happen right away and sometimes everything will seem fine for years even until one day something clicks in one of the tort heads... and then again with some groupings it never seems to happen.
Having as large of an enclosure with as many visual barriers will lower a lot of the problems. Also having animals more evenly sized match tends to help.