Just a suggestion, place a demo pay button on the homepage so visitor can know what it looks like without registering an account. Might probably gain more interest and conversion rate.
I'd consider answering these questions either as documentation that goes through all of the options available on the backend and/or as a walkthrough of the complete process from signing up to getting an order. A demo Trolley account that's set up with a Stripe test key wouldn't be a bad idea either.
FYI though - yes, you can choose whether to collect billing & shipping info at a per-product level.
The buyer and seller both get notified by email (and if you have the Stripe app as a seller, you'll get a push notif). The charge gets fully logged in the seller's Stripe account, with all metadata (so if you ever disconnect Trolley you don't lose anything about your customers)