Your batteries will wear out a lot faster due to false positive activation of camera. You already know that however. There is no specifications for how much of a drain as each cameras situation will be different. False positives will be blowing leaves, shadows, insects, small animals, etc. You’ll also detect items that are further away.
Bottom line is try it, play with settings, see what you get. The batteries are 1 dollar nowadays if you buy them online in bulk quantity. Experimenting is inexpensive. What will bother you faster than the batteries wearing out, is all the video clips you;ll constantly be deleting. 4 to 6 is the typical sweet spot for motion detection sensitivity setting.