As a lifelong snorkeller, never a scuba diver or freediver, I completely agree with Pete about the preferability of a separate mask and snorkel.
Some adult snorkellers do choose combined snorkel-masks if they absolutely must have the option of nose breathing or if they have issues with snorkel mouthpieces, which may cause a gag reflex in a minority of people or tend to rub against the gums when worn over an extended period. Otherwise consider keeping the mask and snorkel separate.
You state that you are "looking at snorkel masks to make it even easier to drift about while viewing the site below", so I am assuming that you are not planning to do many, if any, sorties below the surface of the water to investigate more closely what you will be observing face down on the surface.
Like Pete, I too purchased a twenty-first century version of the snorkel-mask, also out of curiosity, and I too balked at the cross-straps at the rear of the head. From the range I saw online, the differences between the models have to do with how many snorkels they have, where the snorkel entry point(s) to the mask is/are and whether the snorkel-mask covers the mouth as well as the nose and eyes. There are fewer snorkel-masks with eye/nose coverage only than there are snorkel-masks with full-face coverage, enclosing the mouth as well. One example of the former below:
Like conventional dive masks, snorkel-masks must fit individual faces; there is no such thing as "one size fits all". To their credit, manufacturers usually provide three different sizes and show how facial dimensions must be measured so that you are more likely to find the correct size.
I collect the older versions of snorkel-masks and my current collection stands at 25 models. If you are curious enough to want to see them, you will find
an illustrated PDF file of my collection online. I haven't snorkelled with any of them.