When using the Forcepoint CASB, and you are a remote worker, basically not in the office, you have to have an agent on your computer, a Forcepoint agent. However, with many other CASB solutions, they can integrate with MDM.
There are various modules to secure a public cloud, such as Cloud Security Posture Management. You might have seen these features available if you've reviewed solutions like Zscaler or Netskope. A full-fledged CASB should be manageable. However, the tool does not seem to offer complete public cloud visibility. While it provides some cloud visibility and can manage API traffic for Web 2.0, it lacks a specific module for securing public cloud environments.