If you feel overwhelmed by the sheer splendor and magnificence of so many balloons then individual balloon kn5s can simply be deleted from the track folder (or renamed) to reduce the numbers - the models.ini doesn't need to be edited.
The balloons and blimp have slightly randomised starting positions and I've done my best to ensure that they won't clash with each other at the extents of the randomness, but if you do notice anything odd or just want to try repositioning any balloons then just put new figures into this line for the dynamic object (balloon) that you want to move (this is an example, the actual numbers will differ):
RND_POS_CENTER=135, 200, -850
(the first and last numbers are coordinates of the balloon in metres relative to the track 0,0,0 datum as viewed from above, and the middle number is the height of the balloon in metres above the track datum).
If you like a particular balloon design then that model can be used individually to replace an existing balloon on tracks that already have balloons. Simply copy the balloon to the track folder and rename the balloon to match what's in the models.ini for that track.
Thirty balloons not enough for you? Simply edit the models.ini to add more. Balloon models can be referenced more than once without issues. First to a thousand wins a balloon with their face on it.