See other threads about it, but no solution that may apply to me.

Just installed AoW:SM, and after dealing with Comodo to let both the setup and the game do what they want in registry and with inter-process memory access (why they need that, no idea) but blocking the setup from connecting in the firewall (what the... ?), I could start the game, start campaign, see even the scrolling text in the intro animation barely stutter along, and animations are one frame out of however many once playing.
That was first with Direct3D enabled and color cursor. Then went back to setup, disabled Direct3D, switched cursor to software too (but did it both with and without this change and seemed to have no effect), mission start text scrolls smoothly now, that animation above it is also fine, but once in the actual game, animations are still the same.
Tried switching to windowed mode too, no change.

Win 7 32-bit, just a Pentium G3440's integrated graphics.

So, any other ideas?

PS: Played AoW1 on this computer back in 2015, no issues with it. Also no issues with AoW2, also on Win 7, but that was on the old computer, with a GTS 250.

Try going into AoW2:SM's .exe file properties, then into its settings and put it into 16-bit reduced colour mode? I've never had your problem, but when I did that I finally realised I'd beeen missing out on range, aoe indicators, and also many other glow effects.

Sorry for the late reply, but can't find any 16-bit mode anywhere for it. In my case those things appear with Direct3D on, they don't in software mode.
But now it doesn't run at all anymore. Ran 2 days ago (choppy, but it's not slow, just displays one frame out of however many but the game itself goes at normal speed, so playable), didn't try yesterday, tried to run it today, nothing. Black screen, regular mouse cursor. Check task manager, takes up about half the RAM it should and sometimes (not each time I tried to start it) very little CPU. Normally when it runs it takes up a full core for some reason. Try various times and it will get to the full CPU core load, but still half the normal RAM, and nothing actually working.
Found a log file entry saying "ACTIVATE PRIMARY DC - DirectPlay Error - DD: An attempt was made to set the cooperative level when it was already set to exclusive. (ERROR $88760245/-2005532091)"
I'm not aware of having done anything that may have affected it yesterday. Meh.

PS: For either issue, also tried running in a window. I mean, had been trying that with alt+enter since the get go, but now also selecting window from setup. No change.

Oh yeah, forgot to say, apparently what I found somewhere else is true: AoW:SM has issues if the computer hasn't been rebooted in a long time. After a reboot, it's smooth and normal, and those who turn off or reboot daily or even weekly won't notice any issues. Probably goes 2+ weeks with no issues but unsure, as I hadn't tried to play in a while and when I tried again I was close to 3 weeks after reboot, and there was a little stuttering, but far from what I had before (when, due to the lack of relevant updates in Jan and Feb, I eventually ended up at 3 months between reboots).
So basically it seems to be something that only people who leave computers on and don't reboot for a very long time will experience, and even so even a reboot a month should keep the game at least playable, if increasingly choppy during the 2nd half of said month. I was at well over 2 months when it stopped working altogether, which would probably be extremely rare on Windows.