I want to get some spare inner tubes for my new road bike, but I'm unsure what size to get. On my tire it says the size is 700 x 25c and I know that 25 is the max width of the inner tube. So should I get 700x20-25c or 700x25-32c? I'm guessing 700x20-25c would be the safer option, correct?
As long as it is in the range you are good. You can even cheat outside the stated range a bit. Too big and you can fold. Too small and you stretch. If it is spare you are going to carry on the bike then the smaller.
Either of those inner tubes are fine for that tyre. I'd recommend the smaller size since it's easier to get in the tyre without folds or twists.