That's exactly one of my use cases, I have setup runner for 2 projects last week and action runtime went down by a large margin, from 10-15 to 3-4 minutes.

I use single dedicated server that costs ~40EUR/month, AX41-NVME, and each runner is a separate user account to allow for some isolation.

Depending on your setup, you might need to spent some time adjusting jobs to have proper setup/cleanup and isolation between them (but it's not really Hetzner specific, just general issue).