Sorry I'm ignorant but what does NG mean?

New Game, as opposed to New Game+

So what changes whether you do a run with NG or without NG

New Game is just, like, starting the game from the beginning as if you've never played it before. NG+ is starting the story over with all your suits/gadgets/skills etc.

Thanks. If I wanted to do a speedrun should I record it with the timer and then where should I send it?

You can record without timer, I think as long you have video evidence it should be good. Post it wherever you like on Youtube

ok, Thanks