Certain dipswitch settings have different effects on the game (for example, Practice Rank makes the qualifying lap easier or harder, Extended Rank adjusts time extensions AND the speed of the car depending on rank).

You can read a table of the differences on here:

https://www.arcade-museum.com/manuals-videogames/P/Pole_Position_TM218_7th_Printing.pdf

Obviously this is just a 'for fun' board but the settings do affect how the game is played and how difficult it is.

The best settings should be used which I believe are also the default settings.