Hii Adarsha!
It depends on your choice and preference of the state in which you want to take admissions and avail your 85% all india quota seats or reservation. You have the domicile of Himachal Pradesh so you can definitely fill up Himachal Pradesh as your state in neet application form. But, as you say, you did your class 10th and class 12th in delhi, then you must be having the bonafied certificate of the institution or the state. You can avail 85% all india quota seats on this too. So whatever you like, fill it.
Hope this helps.
Good luck!