I would suggest if you are working with Windows plugin users, that you all install the same version of the plugin. Then you should be able to freely swap and share .lxo files. You should also be able to load .lxo file saved from Windows 2020.1 versions of the plugin, although it will not pick up the Octane 2020.1 specific nodes and pins.It's very annoying for my work because I work on projects shared with windows users who have installed the 2020 kit for Modo and now I can no longer work with them.
As far as strategic decisions such as Operating System choices and rendering hardware, my recommendation would be to either move to Catalina/OctaneX, or Windows/Linux with NVidia cards. I can no longer support plugins for High Sierra.