In the menu beta, there is significantly higher GPU overhead. In some cases, the frame times are ~1.5ms worse than live on my 1070ti.

It worsens after you open your quick menu for the first time and hover over something, and stays permanently until you join a new world.

Here's a video showing the problem, I tested 3 different worlds and you can see consistent losses in performance for each one. It is laid out in a way where you can easily pause and see the immediate differences between each version's GPU frame times.