See photo. There is the main roots, but then there also appears a nodule with small roots several inches above? (or maybe these were tiny vines?) What is the starting point above ground?
If these are ungrafted, which is what they appear to be, it doesn’t really matter how deep you plant them as long as the roots are covered and there is at least one bud above ground. Any nodes that are buried, and often parts of the stem as well, will produce roots. You can bury the nodes with roots if you want, or leave them above the soil surface. The more important thing is to make sure none of the roots are bent in the hole (roots can be trimmed back to a few inches with no issues if they are too long) and to cut the aboveground portion back to a few buds.
Commercial vineyards here will pile soil over newly planted vines to protect them from desiccation until the shoots emerge, but we are usually planting in late April or May when it is already beginning to get warm.