Offer negotiation help

Since we all are actively interviewing at times, I need help with how you go with offers. I was interviewing for last month, have got two offers and few companies are still in the pipeline.

How do you go with saying no once you have accepted an offer.

So i got an offer from a startup they are paying higher than the other one for now, but i still wanna try with other companies.

They have mentioned about sending me the laptop, can you please help me with the process, this is my first time switching.

Current base 36 Offered 47+15% variable+ esops Yoe: almost 4