Just got 4.20 and gave it a spin.
Going with sunny 16, you’ll want something like 900,000 Lumens for simple room point light.
There are two new options added to PPV, “Maximum Aperture” and “Number of Diaphram Blades” which you can’t use because they’re both grayed out.
It’s very strange I have to say, that Epic adds two new options to physical lighting system as if the system is usable and they’re upgrading it.