For secrets, I self-host Infisical on the box -- easy to plug in whatever secret manager, should make it pair nicely with https://github.com/tellerops/teller or something similar
Had no problems with Hertzner so far, just enjoying the raw CPU power of bare metal. The plan is to roll out more boxes across different providers, using Tailscale for the backplane network and Cloudflare to load-balance between them. All in due time What issues have you been having ?