Tunnelblick is "just" a GUI — a front end for OpenVPN. Each Tunnelblick VPN Configuration includes an OpenVPN configuration file (a file with an extension of .ovpn or .conf) that Tunnelblick tells OpenVPN to use to make a connection. The details of how OpenVPN should connect using the configuration are contained in that file.
OpenVPN files are plain-text files that contain the instructions for OpenVPN to connect a client to a server or run a server. There are dozens of options for these files. The primary documentation for them is the OpenVPN 2.4 man page and the OpenVPN 2.3 man page.
There is also a list of OpenVPN documentation.
There are also many tutorials about setting up OpenVPN available on the web, just search for "openvpn configuration", "openvpn tutorial" or "openvpn tutorial macOS".