When a mob is both rare and elite only the rare icon shows. To remedy this elite mob levels should display '{mob_level}+' instead of just '{mob_level}'

I have a fix for this ready but don't have permission to push my branch. It's pretty simple. Change TidyPlatesCore.lua:623 from:
visual.level:SetText(unit.level)
to

if unit.isElite then
  visual.level:SetText(unit.level .. "+")
else
  visual.level:SetText(unit.level)
end

There should be a different coloring for rare and elite mobs (gray and yellow, if I remember correctly). Does that not work?

It does work but if a mob is both rare and elite the rare color overrides the elite color. So the color is gray. This makes it so there is no visual difference between a regular rare mob and an elite rare. Similarly I'm not sure that just making the elite color override the rare is a good solution as there would then be no visual difference between elites and elite rares.
I think there needs to be two separate indicators instead of merging them. One for rare and then another for elite.

Any updates on this?

Working on 9.2.0 currently, so there's is not much time currently. I'll take a look at it once all features in 9.2.0 are working as intended.

So, I played around with showing two icons, one for elite mobs, one for rare mobs, but that does not work I think. It takes up to much space on the healthbar and does not look good. Instead, I added a seperate color for rare-elite mobs (bronze).

Adding a + to the level would also be possible, but it's something that also is not part of the default unit frames, I think. Rare-elite mobs show with the actual level there, if I remember correctly. So, I am not sure if people would understand what the + means.

This version will be part of the next beta version, out today hopefully, so that you can test it.

I might be wrong regarding the +, I think. I find it hard to find a rareelite mob these days, but elite mobs do have a + before there level.

So, adding something like you suggested might be correct:

visual.level:SetText((unit.isElite and "+" or "") .. unit.level)

A bronze star would be perfect, I think. Just some visual distinction between the three. For testing there's a rare elite that's in Windshear Crag in Stonetalon Mountains that usually hangs out around 65,54 in Classic. For most text based addons (tooltips, some unit frames) the common denotation for rare is 'R' or 'r' and elite is '+' and for a rare elite is '(r|R)\+'.

With v9.2.0, there is now a different color for rareelite mobs as well as a + sign before the level text of elite units.