Only my index page isnt publishing correctly.

[Pablo]

If you use flexible layout, then it should be for the entire page, including the master page.
However, you can also use (floating) layers to mix it with absolute/fixed content.

[waynethetodd]

Got it, so I can use a floating content placeholder that contains static content with a master frame that uses a flexible grid layout?

If so, would you recommend using a Flex Grid or a Layout Grid for the master frame?

[Pablo]

Flex grid or layout grid is your personal preference .
But if you are not familiar with flexible layouts then I suggest to start with layout grids, because they may be easier to use.

[waynethetodd]

So, as I understand, using static content inherently will give me inconsistency between what is shown in the editor and what is actually published?

That seems to be what was explained to me for the odd behavior of my photo gallery. The way we've set up our websites, it would take MONTHS to take everything and move it into layout grids.

[Pablo]

So, as I understand, using static content inherently will give me inconsistency between what is shown in the editor and what is actually published?

Correct, because there is no pixel perfect way to render text the same in all browsers.

The way we've set up our websites, it would take MONTHS to take everything and move it into layout grids.

In that case, you can try my other suggestion.

[waynethetodd]

When I set the content placeholder to "floating" it sticks to the top of the page, ignoring everything else. Is this intended? https://imgur.com/a/9pdtJbV

So at this point, would I need to use grids anyways?

[Pablo]

This is intentional. All floating elements start at the top of the page.

Related tutorial:
http://wysiwygwebbuilder.com/layout_modes.html