I'd recommend you to use the first one, which creates a LXC then installs syncthing there. At least I like this approach, never install anything in the proxmox host unless is necessary.

Seems the second installs syncthing directly in the host (or wherever you are logged).

Edit: I know those tteck scripts come handy, easy-to-use that's ok to test but I always better understand what any online script is doing before running specially if running as root. Just a reminder to be careful...

Have fun :)