Hi John and welcome
With Soundtrax you can import multiple tracks without problems, and adjust speed without changing pitch etc. From the Start Smart window, select Soundtrax, then select Multi-track Project.
With the multi-track page open, select the first track, right-click and add the audio you want. Then select the second track and add the other track. many tracks can be added this way. You may need to drag the tracks left to get them to all start at the same, or desired, time. If they are out of sync or timing, then right-click the track and modify the properties. It could take quite a lot of fiddling around until you get used to it.
Have fun and let us know how you get on with it. DonÂ´t forget to put the player-cursor back in the start position of the track when you are ready to test the effect of what youÂ´ve done.