Thinking of getting SWAT 4 on GOG as I no longer have a DVD/CD drive in my desktop. I am wondering if this version is fully compatible with mods such as Sheriff's Special Forces (SSF) and whatnot? How does multiplayer work, if at all? Will I have any trouble if I am on Win 10 Pro 64bit?

No problems with anything here. I got it again too because the DRM on my original version was such a PITA. I think I had to edit the ini for full resolution but that's it.