Hello!
I upgraded my engine to use PIXI v6 instead of v4 and noticed a significant increase in the drawing time (especially pronounced in iPad 6th Gen).
Left is V6 and Right is V4, in the same scene.
I originally thought it was a problem with the getLocalBounds call in spines that I had in the render loop and managed to improve the scripting time by about 10% but I then noticed that the rendering and painting had increased dramatically... the same game that runs at 30-40fps with V4 runs at 15-25fps with V6 in an iPad.
Weirdly though, the draw calls in V4 were about 170 and in v6 dropped to about 60 (checked with spector.js chrome extension) which would indicate to me that the fps would be better but they are not, sadly.
Setting 'transparent' to true or false when creating the PIXI.Renderer does nothing 😕
Is this a known thing? I searched for days and could not find anything about this 
EDIT: I can send the Spector.js reports for V4 and V6 if it helps but they are too big to be embedded here!