Multiple Text field layer

It's actually possible to attach fields to a layer. InDesign offers this functionality.

Also, I wrote a tool for it, and the download is here:

(however it is for members of the site)

https://www.pdfscripting.com/public/programs/downloadsearch.cfm?searchtype=simple&searchmode=cat&keywords=recent&sortby=name&cat=Acrobat%20Plug-Ins

Otherwise, if you want to simplify the messiness, then generalize your approach to the solution by making more it more indirect. You haven't said, but I imagine you've brute force hard coded the hide and show operations. A neater approach is to use an object to store the field/text configuration for each selection. This separtes the operation from the configuration data. So now the configuration data can be written in a way that is easy for you to both see and modify. 

for example:

var oDataConfigs = {"Dropdown Choice 1":[{bField:true, cName:"TextField1", bHidden:true}, {bOCg:true, cName:"Layer1", bHidden:true}, .... etc....],

                                   "Dropdown Choice 2":[{bField:true, cName:"TextField1", bHidden:true}, {bOCg:true, cName:"Layer1", bHidden:true}, .... etc....],

                             };

This is just an example data structure. It could be organized in anyway that makes it easier for you to code. 

Now your dropdown script is written to use the data structure instead of being hard code. Makes it easier to maintain.  

Fields and layers exist separately from one another (for the most part), so it's not an either/or situation.

If you want to change both the static layout of the page and the interactive elements in it you need to show/hide both of them, independently of one another. If you name them correctly, though, this shouldn't be too difficult to do.

It's not very understanding what you try to achieve from your post.

Why would show/hide fields be more messy than show/hide layers?

Couldn't you use the same fields and change what text is displayed depending on choice?