I am thinking about other yarns for the overshot scarf project. Would tencel or bamboo work as the warp and weft to create a very soft scarf?

I think that as long as you use yarns that are about the same gauge that Jane has recommended you will be fine. I do a lot of yarn subbing to try to use what i have on my shelf. I too am going to try different yarns on this project. Jane had some suggestions for subbing in the video that were helpful to me. But, i go in fully understanding that there is no way to know until my work is off the looms and wet finished. And when i make drastic changes to the yarns, I usually make a smaller warp unless i truly know the result will be what I want.