You will take three PFTs at OCS. Initial, one in the middle, and a final PFT. You must get a first class on all of these, but at least 60 points in each category. So no, you can't get 100 points for pull-ups, 100 points for crunches/plank, and then 35 points on the run. I believe "in the fleet" this is different, but don't be the officer that doesn't get a first class or isn't well-rounded in all three categories.
The PFTs are graded events as well. You can get sent home if you don't get a first class! A 235 is equivalent to 80 points for your grade average, and a 300 gets you 100 points. The other scores are in between those numbers on some sort of scale. At OCS, minimum passing grades on everything is 80 points. At TBS, it's 70 points so don't get confused.
I really recommend doing pull-ups instead of push-ups. Not even just because push-ups don't get you full points, but because after 2 minutes of push-ups, it's much more difficult to do planks or crunches.
If you are already selected to go to OCS, I'm sure you know about PFTs. If not, here are the standards.
Be careful using online PFT/CFT calculators, some of them are inaccurate. I will go through a few of them to make sure they are correct before I link them here.