It should be no problem getting X11, OpenSSH, and most other programs working together with various operating systems (Including FreeBSD & OpenBSD).
Xorg is still Xorg no matter what OS it runs, the same applies to OpenSSH and most other applications. While details, versions, and default configurations may be different, it is conceptually the same.
If you want a more specific answer regarding your X11 forwarding: Ask a more specific question
