@René-Zuber What you're probably looking for is segments.
Only the OSM map currently supports segments. Using segments we can change route settings for certain parts of the route.
I.e.: WP1 to WP2, use fastest and wp2 to wp3 use most curvy, then wp 3 to WP 4 use fastest.
There are some tutorials on how to use it. It is too much time consuming for me to show it here, but it definitely works a charm.
Note that you probably want to switch back to HERE/TomTom as soon as you've set your "fastest" part of the route, but make sure to EXPAND your route first with enough waypoints so that the segment route setting is replicated by the additional waypoints.
I would advise to finish your route in OSM untill you've made it to your liking for about 80 to 90%, then expand, and then convert to Here or TomTom.