As for beta vs. stable, Cloudflare Workers is generally somewhere in between. Every 6 weeks, Chrome and V8's dev branch is promoted to beta, beta branch to stable, and stable becomes obsolete. Somewhere during the six weeks between verisons, Cloudflare Workers moves from stable to beta. This has to happen before the stable version becomes obsolete, otherwise Workers would stop receiving security updates. Generally there is some work involved in doing the upgrade, so it's not good to leave it to the last moment. Typically Workers will update from stable to beta somewhere mid-to-late in the cycle, and then that beta version subsequently becomes stable shortly thereafter.
(I'm the lead engineer for Cloudflare Workers.)
OpenWorkers is really aimed at a different use case: running your own code on your own infra, where the threat model is simpler. Think internal tools, compliance-constrained environments, or developers who just want the Workers DX without the vendor dependency.
Appreciate the work you and the team have done on Workers, it's been the inspiration for this project for years.