The main difference lies in investor accreditation and solicitation rules. 506(b) allows for a mix of accredited and a limited number of non-accredited investors without general solicitation, while 506(c) permits general solicitation but requires all investors to be accredited.
This means that once you complete your raise, only you will have access to the investors you've brought to the platform. They'll never be marketed any other opportunities by us.
Yes, non-accredited investors can participate in Reg. A+ offerings.