In terms of hardware: I think if you are just starting, use what you have. I have a Synology, and OH runs fine on it. However, I’m considering to invest in an Intel NUC (with Ubuntu) so OH runs on an independent machine. This way, Synology DSM upgrades don’t impact OH anymore, and I’ve also noticed some drops in OH performance when multiple computers were backing up to Synology. I’m slightly reluctant to use Raspberry, I’ve read too many posts in this forum related to corrupt SD cards.
Related topic: https://community.openhab.org/t/best-hardware-platform/