Hello there. Last month, I had a 7 days trip to Himachal Pradesh and from my experience, I could tell that there are way beautiful places to visit in Himachal keeping Manali and Shimla apart. Let's proceed in a circuit ok. There are two starting points to Himachal i.e. Manali & Shimla. People prefer to start from Shimla as the roads connecting to Spiti are quite good. But we chose to proceed in reverse direction. Talk about small villages, Key, Kibber, Hikkim, Komik, Langza, Dhankar, Tabo, Kalpa, Chitkul are some of the best places you can visit during your trip. Each place has it's uniqueness, for example in Tabo, there is Gue monastery where a 500+ year mummy is being preserved. Also you can Google to get detailed description of these places.
Shimla and Manali are beautiful but also crowded and that kinda ruins the fun when you are looking for a getaway. But there are so many small wonders in Himachal that are untouched by crowds. Kasol is the base for a lot of them. Kasol itself is crowded but you have to go there to get to the other crowd free ones. One of them is Tosh, you might have heard of it. It is the base for Kheerganga trek and it is beautiful and calm and serene. You can also trek to the Tosh glacier.
I suggest you go to Rasol and Chalal. Rasol is 10000ft above sea level and has such a beautiful view of the Himalayas that you cannot forget. It is also not known to many. It is good 4 hour trek and every moment is memorable.
A must go to is the Malana village. The road is tricky, and bad and rocks fall but what lies beyond is worth it. Waichin valley lies 4km above Malana and you will not find another place like this. The amount of stars you see at night and if you're lucky you might see a falling one. Magic valley is higher than waichin but you cannot stay there as there are no homestays or campsites. You even find a glacier up there.
But keep in mind you won't find much network coverage in the area, both rasol and malana.
In malana there is no electricity even. They use generators only for a few hours a day. Areal mountain life is waiting for you