I was playing around with the scalers in order to improve the pixellation (I could barely read the log file), and found the perfect scaler in case anyone else wants to use it:
Open up DOSBOX.CONF, and in the render part, edit "normal2x" with "advinterp2x".
render
You could also try advinterp3x, but I found that slows down things.
Now everything is very smooth, text is also much more legible!