I think I found the reason why drawing in the maximized envelope is causing lag, it is because the mod envelope ( antialiased one ) is still active altough not visible .
Go to mod.section of instruments, choose envelope select full screen …and draw …some lagging occurs ( not much ,but compared to 2.8 it is annoying .), you also notice that altough is now full screen , you can drag the left border of he env.window …you’ll notice that this env. window is just a winow stacked upon the mod .output env.
Now detach the envelope and adjust the size , go to pattern editor and draw in the detached envelope …result much smoother drawing