You are using clothing for the wrong Genesis model, Genesis8 clothing needs to be adjusted to fit to the Daz Genesis2 model that vam uses and be in a t-pose position. The clothing importer in vam wraps the shape of the clothing to the nearest vertex on the model, so if it's not in the right place to start with you get weirdness like this.
You need to adjust the pose and shape of the genesis 8 figure in daz to match genesis2 while they are wearing it. Then export the clothing as an .obj and re-import it to lock in the new shape and save a scene subset.