Hi,
I tested it with duke layout and I dont have problems. In triad options I set mouse sensitivity to maximum, and in magic dosbox’ mouse options I set sensitivity to 400. Now you can aim with mouse well. Left joystick uses keyboard kes for strafe to sides and forward/backward. Aim with mouse.
The only thing, tweak, what I recommend is to place special widget configured to “block y mouse coordinate”. It toggles mouse movement forward/backward, what can be unwanted by aiming.