The GraphQL api in Redwood is powerful, yet simple - so you would build your backend in Redwood, and have your angular front end make gql queries like you would with any other backend.
Redwood's GraphQL API is built on Yoga (we collaborate tightly with The Guild) — https://www.graphql-yoga.com You just need a GraphQL Client, which The Guild already has an option ready for you https://apollo-angular.com (Note: Apollo or other clients fine as well.)
Here's an example "How To" about connecting Next (React) with Redwood: https://community.redwoodjs.com/t/how-to-connect-a-next-js-f...
I'm a co-founder of Redwood and help lead the project so I can say as a matter of fact we a highly collaborative and enjoy (and support) exploratory projects. It's a priority for us to better demonstrate the power of Redwood's API through examples. If you'd be interested in digging in collaboratively with the community, I can help connect the dots. Just kick things off over here and tag me @thedavidprice: https://community.redwoodjs.com
No pressure at all! Just wanted you to know the invitation is open. Anytime.