Can I run OpenClaw in a VM and what are the requirements

Yes. Treat a VM the same as a VPS: it needs to be always on, reachable, and have enough RAM for the Gateway and any channels you enable.
Baseline guidance:
Absolute minimum: 1 vCPU, 1GB RAM.
Recommended: 2GB RAM or more if you run multiple channels, browser automation, or media tools.
OS: Ubuntu LTS or another modern Debian/Ubuntu.
If you are on Windows, WSL2 is the easiest VM style setup and has the best tooling compatibility. See Windows, VPS hosting. If you are running macOS in a VM, see macOS VM.