I love this game so far. Question, when a new update comes out do I have to redownload the whole thing or just an update? And will my saves carry over?
You can always keep your save files.
On android, you have to download the new apk file and install it again. It'll automatically update your game without changing your save files.
On windows, you can use the "update files only" from the previous to the newest version, but make sure you don't skip an update or you'll be missing files! Else, you can always download the full game again and copy the content of the save folder from the old game to the same folder in the new game version.
I made a video about update files and moving save files here: