Dotting this; I really want to be able to play my kids in this across two computers, but I don't know how to set that up.

So I don't know exactly what you're referencing here, but I can tell you this.

If you have a CD version of W2 battle.net, and you download a copy of the GOG W2 battle.net, they both work together just fine (Note I'm only testing Windows). You absolutely do need to have the IPX wrapper in your installation folder on both, but once you do it's business as usual.

I already had the IPX files in my CD version of W2BNE, so I loaded that on PC A. I downloaded the GOG version of W2BNE onto PC B. I could launch into both the classic and new launchers on the GOG version, and I tested doing both an enhanced game and a classic game. It works exactly as intended and the games are seen instantly on the other machine. Note this is on a LAN, as the IPX wrapper itself does TCP/IP broadcasting.

So long story short the GOG version of this is basically the same as the original CD version. What I'm not sure about however is if it's possible to play battle.net versions against the original W2 or ToD expansions. If you can find info about people doing that with the CD versions, then the GOG version will likely work the same.

Side note if you don't have the IPX wrapper for your CD copy, you should be able to just copy the six ipx files from the GOG version and place them into your CD version. There shouldn't be a need for configuration unless you have multiple network adapters enabled.

EDIT: I think you were specifically asking if there is a TCP option inside of the game itself. That is not the case. So if the mac version only has a TCP option, and the Windows version only has the IPX option, chances are those two won't work together.

Windows has these choices:

Battle.net (Only in the classic launcher)
Direct Connection (Null modem cable)
Modem (Dial up)
IPX Network (Requires an IPX network adapter to use. GOG bundles in a wrapper so this option works using IPX, but the traffic is passing over IP)