Most pictures I have seen of Lophophora, only a flat button pokes out from the substrate, the majority of the cactus is underground.

I'd like some advice on how deep to plant Lophophora that I got in an un-planted state.

One seems relatively straightforward, it has a clear horizontal line on the body of the cactus where the plant is green above, and has a grey, barklike texture below (and below that the root section).

I'm gathering it's safe to treat this line as the plant's preference for planting depth. However, I'm curious if it's beneficial to plant a little deeper?

However, I have another plant, that has this division in a sort of sharktooth-like pattern, so I'll either have green skin underground, or the grey barky skin above ground. It also has a healed wound in this area where it seems like the previous owner removed a scion for propagation.

I'd like some expert input on whether it'd be better to only have green above the substrate, or to have none of the green under it? Planting deeper would definitely be the most aesthetic solution, but I'd like to be sure I'm doing what the plant 'wants me' to do. I'd rather have a happy cactus than a sharp-looking topiary.

ps. For substrate I'm using a quick-draining mineral-only mix, so at least according to my hopes, waterlogging won't be an issue.