I'm going to answer this question a little differently, because enforceability can also depend on facts and circumstances. Think of the binding / non-binding distinction as more of a social commitment signal. The No Shop means that once the company and investor both sign, they're pledging to work together to figure out this deal along these high level terms for the next 30 days. They've made a commitment to each other. Venture is a relatively small community and going back on your word gets around. Social consequences can be just as bad as legal ones.