How to turn down a job offer without burning bridges? Pls help!

Got a job offer for an AVP position at a small boutique covering diversified industries. I wasn't too impressed with comp but was willing to go if I like the team enough. I've now spoken to a few people on the team across a week and half since getting the offer. The team seems nice, but just wasn't feeling comfortable enough with what I was seeing to take the offer. I want to give the senior lady (who is the one I've been in contact with) a call to decline, but I want to craft the right message so as not to offend or burn bridges. She was very excited to have me on board (due to my solid experience but also we're the same obscure ethnicity), but she is aware I'm not too comfortable with comp / culture. I don't want her to be mad that I dragged this out to a week and a half, but I really was trying to just get comfortable. Should I go generic or specific on why I'm declining?

Also, am in two other processes right now with banks. I haven't mentioned that to her - just didn't want to say more than I needed to and she never asked. I will likely take one of the other ones as team seems great and comp is significantly better. Should I mention that I'm taking another offer? I don't want her to think I was leveraging her offer to get the other ones because I wasn't - haven't even mentioned to the others I am in other processes.