Hello,
You can leave all DOSBox settings at default, except for the cycles setting.
Cycles of 30000 or higher is recommended for the best experience, but you can play with less.
20000 will be mostly ok, even 12000 is ok if you turn off the textures in the game (toggle using T key during a racing session).
You can also set cycles to max to get the maximum performance your CPU can offer. This can sometimes cause minor sound glitches.
core = auto
cputype = auto
cycles = fixed 30000 (or cycles = max)
To check if the cycles are set properly, press and hold the O key during a race.
The P.O. value should never go above 100%. It should mostly be very low.
Otherwise, check if you set the proper frame rate in the game itself:
Game Options Menu > Game > Frame Rate: 25.0
Cheers