Can different pricing models run side by side in the same store?

Yes. Retail, B2B contract, member, and no-payment pricing all resolve against one master price book in one storefront.

Yes. One storefront can serve retail customers at list price, B2B accounts on contract pricing, members on member rates, and internal users on a no-payment flow, all at once. The price each visitor sees is resolved from the customer group and account they belong to, against one master price book. You are not running separate stores or separate engines to support different commercial models under one brand.