As far as I know, you technically have to type tsu on the keyboard when typing kippu to change tsu to the smaller version.
When typing "kippu", you type ki and tsu but hit a button to change tsu to the small version then type pu. Just wanted to clarify unless there's another way to get the small tsu.
つ is different fromっ. The lowercase tsu extends the next consonant sound. So instead of kipu it's kippu. Slight but crucial. There is a counterpart of this for lengthening vowel sounds. ー and 〜 are sometimes used to lengthen the following vowel sound. For example かーし vs. かし (Both mean the same but the first is pronounced kaashi and the second kashi. I don't know what this word means and probably isn't the best example but it gives you an idea)