I fired up MOO2 and the mouse speed in the main screen is a bit quick but doable but the tactical combat layer is insanely fast. I spend more time correcting for the “overswing” of the mouse scrolling than i do commanding

Im sure there is a line to modify for dosbox, but not sure which or what starting point i should use for the adjustment.

Any suggestions?

suggestion is to install 1.50 patch. tactical combat scroll speed is fixed there and configurable.

Is that an official patch?
Does it change anything else game wise?

No but GOG's version already comes with an unofficial patch albeit a much older one. ONLY if you so wish. You can choose between: as close to vanilla as possible but with bug fixes; a slightly improved, as if the original developers had released one more patch; all the way to mods that change the game a lot.

Highly recommended and I am not one of the team who worked on it unlike Rocco.40 above you (with 2 others).

certainly, it's an extensive patch, see thread about it on this forum if you want to learn more