Tints never damage the defogger, those r just myths about tints ruining the defogger, i get all my car tinted and never had a problem with defogger. but dont get the Rs600 cheap korean tints, they get scratched within a month and look terrible, there is a good german paper which has a dark blue shade, (Had it pre installed in my Jdm Alto, also available locally) You can get the whole car done for about 5k, but if u want something really good and wanna spend 10k-20k go for 3m 
In my opinion the 5000 works best and the shade is exactly the same as in the picture above, it is scratch resistant
