Go to Chitkul. I recently went there. The place is paradise with all the details how I went, mumber of days, where did I stay. And if you ar eleft with any question, let me know. And as you said, you have one week so, please do not waste it by going to Rishikesh.
That's cool idea, you can travel several places in himachal and uttarakhand. In himachal you can visit shimala, spiti valley, Manali and many more. You just have to visit there and with the help of locals you can easily get navigation for best spots If you are planning to trip uttarakhad and especially in chamoli,uttarakhand you can contact me . I'll provide you local guides and best places to visit like valley of flower, hemkund, lord curzon trekking contact me on WhatsApp: 8410007524 ( laxman negi ) or mail me on: firstname.lastname@example.org