For the guest room, choose vanity that has just basic features but large enough to be completed with two sinks.
What guests need in the bathroom commonly is not that much, compared to what the homeowner want and need in the bathroom. You know, a guest may stay overnight for one or a few days. But, to feel every guest like at home, it is better if is completed with some drawers sufficient to store a few things. Some minimalist sink vanity with two sinks is a good choice. Why should be with two sinks? Well, if there is a couple with their little kids staying overnight, that is going to be necessary.
Some ideas of sink vanity are specifically connected to where the vanities are supposed to be located in, because, sometimes, inside a house or some public building, there are more than one bathroom built for some different purposes, e.g. guest bathroom, master bathroom, and things. Also, there may be a powder room that surely requires the presence of some vanity.
Choosing a vanity for bathroom is basically rule-less, but experiences teach us if there are tendencies in selecting vanity ideas that lead to failures or successes. So this means that there are always recommended bathroom vanity ideas that we use as the references.