I am applying to a scholarship, where I need to answer some questions in a one minute long video. I would like to push as much information as I can, but I wouldn't like to make it over-crowded... so what is an optimal speech / time ratio? (how many characters, or sentences, etc for one minute?) Are there some statistics like that? What is it like at ads from tech companies?
You will generally get the following guidance if you take courses on presentation skills (this list from write-out-loud.com)
So you'll probably want to aim for that 150 wpm range to be able to get a reasonable amount across, but not sound like an auctioneer
Do you have the option to display your answer in text on the screen as you're saying it? You could probably speak faster: The viewers would be reading along anyway, so if you were unintelligible for a few words, the viewers would still get the meaning.
I agree with @DrMayhem about speech speeds, but I think you can get away with 175-200 wpm and not sound too rushed. You would have to be focused, though, and it might require a few "takes" before all 175-200 words were clear. If you do try to squeeze in more than 150 words, make sure you vary your pitch (like a musical note) so you aren't just monotone. Energy drinks aren't out of the question. ;-)
After writing all this, I just realize how much of this is a learned skill/art. I've been in theater and on YouTube for years and years, using my voice like an instrument. If you don't use your voice that way normally, and you don't have a natural knack for it, you might want to aim for 150 words instead of 200.