What could be my best option to bridge 2 Lan's?

Hello!

I have a couple of servers, office and home in 2 different physicall lotactions. The servers run the camera's NVR (Xeoma), file services (Samba, syncthing...) and backups (rsync).

I want to be able to access to each lan in a transparent way, just ping to the other subnet without the need to configure each OS or APP.

I have DD-wrt routers on each end, so ideally i could setup everything on the routers and forget about it. if needed i can buy more hardware or buy some rpi's.

Between my options:

- IPsec tunneling

- Open VPN Tunnel (Running on the routers ideally)

- Zerotier

- EoIP

Think OpenVPN running on the routers could be my best option, but im really just an enthusiast and at the moment my network's knowledge its pathetic, so i would really appreciate any advice!