Spiti trip via Shimla

Hii everyone! I will be traveling to Spiti next month for a 5 day trek.

Before arriving in Kaza, Spiti, I am planning to spend 2 days each in Shimla and Kalpa. What do you recommend to do in Shimla for an offbeat traveler? And what’s the best way to go from Shimla to Kalpa? I’m aware there are public transport options available but is there a particular spot from where I can get a shared taxi from Shimla to Kalpa? If yes, how much does it cost and how long does it take?

Appreciate your responses!! Good day!