PM sent.
I'm using GOG.
I found some info that it is a modern AMD driver that is the culprit. I've yet to test with an older one.
I think that we now have enough information to explain why some versions of SMACX no longer run under Windows 10, while other versions do run. The problem is that Windows 10 disabled support for a service named secdrv.sys. This service provides copy protection to games and verifies that the game's disc is in the drive when the game starts. See here for more information. If either game doesn't run under Windows 10, the solution is to obtain a version that doesn't require a game disc to be in the drive. Such versions are legally available. Please post here if you need help finding such a patch.
In this thread on AC2, Lxndr stated that the game ran for him under GOG (which has no copy protection), but didn't run under the PRACX mod. The PRACX mod makes many changes to the graphics interface. I suspect that some of these changes aren't compatible with Windows 10.
Your best bet to get both versions to run is to purchase them from GOG for $5.99. If that price is too high, you can wait. GOG discounts the price to something like $2.99 a couple of times per year. If that option doesn't work for you, please post how you got SMAC, but not SMAX, to run. If it involves using, shall we say, an unpaid copy of the game, please start a conversation with me. You also could install one of the so-called unofficial patches. Many of these can be found at Alphacentauri2. AFAIK, the unofficial patches all are for SMAX, but @Buster's Uncle can correct me if necessary.
Sounds like you have the Win2k patch. That official patch removed the DRM from SMAC, but not (for an unknown reason) from SMAX. (This change wasn't documented in the release notes.) At this point, all I can think of is to install one of the unofficial patches, which also remove DRM from SMAX. I recommend scient's unofficial patch, v.2. This patch fixes many bugs, but doesn't alter gameplay. I thought that CivFanatics didn't allow linking to unofficial patches. However, some digging revealed that we changed our position about 6 (!!) years ago. Please post again if you have any questions or run into further problems.