Question about track rules

The fictional route I am creating uses Scale Rail and all of the track I have laid thus far has been the SP Scale Rail, but I want to change some of this track to ATSF Scale Rail because my route is going to be based off of two Class 1 RR's. Can I do this without causing any major issues? I know there has been talk in the past about using 2 different track rules but since both are from the same creator will it make a difference.