Best practices for inline MathML

Hi, I am porting academic papers (mostly species descriptions and natural history accounts) to ePub and sometimes they have an equation or three. Most are short, e.g.

<math blah display="inline">
<mi>y</mi>
<mo>=</mo>
<mi>b</mi>
<mo>&#x2062;</mo>
<msup>
  <mi>x</mi>
  <mi>k</mi>
</msup>
</math>

That kind of thing, but then the paper will sometimes explain a variable so that there is an inline math node with just a single mi child.

I am having trouble finding best practices for this. What I am doing seems to work well in Calibre, but for example my Kobo puts a huge space in for the InvisibleTimes.

I'm not a MathML guru, I understand there are two competing semantics and ePub viewers often only support the descriptive semantic?

Are image fallbacks really necessary for simple equations that can be described in English?

What method is best for screen readers?

It's frustrating a bit because so much on the web my search turns up says to use MathJax with LaTeX equations but many ePub viewers do not support JavaScript.

https://github.com/w3c/publ-epub-revision/issues/845 is the closest I have come to finding advice on best practices. Is there an actual blog or write-up that details current best practices, even if not official, for ePub with MathML pieces?
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Sent from my Android device with K-9 Mail. Please excuse my brevity.