Lets you choose the Integrator to use for the render. The default, PxrPathTracer is a fine choice for most rendering situations.
See the page for each integrator for information about their settings:
Image Plane Subset: Specify the trace subset for the image plane. The default value is rman__imageplane, and RfM automatically emits image planes as part of this set. The integrator will trace against this subset to get the color of the image plane. This is used for the holdout background. Note that this only applies to geometry that is assigned an emissive Bxdf such as PxrConstant.
Max Diffuse Depth: Number of diffuse bounces for indirect illumination. A value of 1 is usually sufficient, larger values are slower. This attribute can be overridden on individual objects.
Filter: The filter for rendered pixels. The box, triangle, disk, gaussian, and blackman-harris are softening filters while catmull-rom, sinc, mitchell, separable-catmull-rom, lanczos and bessel are sharpening filters. Separable-catmull-rom is a good compromise.