There is two timers: at the top (the winning condition) and when almost grabbed you have a health bar above the flag, which you shouldn't rely on, it's a split second, more of a warning and a leniency feature.
As for strategy, well, it changes constantly, there is not one dominant strategy that will guarantee victory! Some do get close, but the AI is designed to keep you on your toes. It's a game where you have to adapt to the current situation at hand. Sometimes it's worth it to stick around your teammates and look out for cheeky aggressors. Sometimes it's better to bail and run as far as possible. Sometimes you have to do do something risky and jump above the enemies and abuse slow motion to make it easier. Sometimes you also have to use platforms to your advantage to slow down your pursuers. Sometimes you have to rally the team together in order to help them win a team fight and so on.
Thanks for your comment and checking my game out!