Highlighter changes depending on the PDF file in Acrobat Reader

If you have searchable text because it was a computer-generated PDF from a Word file, or whatever, the highlighter will follow the text. The reason why the highlighter "rambles" in the first example is that the text is an image of text and is not selectable or searchable. 

So, the quick answer is no, you cannot by using the highlight tool.

But you can use the drawing tool.

First, look at the Tools, and click on the three dots at the bottom.

 Now, select the option to Customize the Toolbar. Now scroll down the right side until you see "Add Comments."

At the very bottom of that section, you'll see the option "Draw." Click on that and then click on the top icon of a left-pointing arrow. That will move it over to the left side.

 That will add this to your toolbar. Click on Save (it might save itself, sorry, it's a bit strange). When you're done, there will be a squiggle in your toolbar.

Now, when you click on that, you'll see a circle at the bottom. There are two ways to customize this. You can click on the dot and change the color AND the opacity (if you want text to show through)

 If you want to change the line thickness, click on the multiple lines and change the thickness.

That should give you what you want.

Let me know if this solves your issue.