High FPS in LFR but lower FPS in Mythic

[Deleted]

It's normal due to performance profile being enabled, don't forget to disable after making the tests.
Also, do you have an AMD cpu? they has a poor single thread performance which is critical for wow performance.

I have both Intel and AMD rigs, however yes i did test it on the AMD setup. But I still get 60fps on high on the AMD rig so the single thread issue isnt really an issue for me. Was suprised to see ElvUI, DBM and weakauras on top 3 thats all.

[HeiAggra]

Might also be to do with Mythic gear sets and such having additional spell effects and shiney particle effects?

Now the OP say's i use transmorg lol sorry but just come to mind that answer