Path Tracing always as Secondary GI Solver

[maru]

So for interiors we should use PT/4K?

My advice would be: use the defaults (PT+UHD). If you want, you can also try PT+4K, but 4K comes with an "experimental" disclaimer.

[davemahi]

I just want to clarify your response. Would you say this for animation as well?

[maru]

For interior animation - PT+UHD (with "animation (flicker-free)" preset enabled in UHD settings).
You can use PT+PT, but the rendering will be much slower with little visual difference.

For exterior animation - PT+PT. If there is something with lots of GI visible (light bouncing around) it could also make sense to use PT+UHD.
The reason is that if the rendered image mainly shows direct lighting (think of a grass lawn + some trees + cars) then you don't have to compute the UHD Cache as it would not speed up rendering. UHD speeds up anything where there are some clearly visible light bounces (think of a room where the sunlight hits the floor and lights up the interior).

You can use PT+4K (4K with the "animation" preset enabled as well), and the usual disclaimer applies.

More info on UHD and animation: https://support.chaos.com/hc/en-us/articles/4528617365649