LuxRender was a physically based, unbiased rendering engine that integrated with Blender, and LuxCoreRender was its next-generation evolution starting at version 2.0. RenderStreet supported both engines in the past, but they are no longer part of the farm.
If you are starting a new project, Blender's Cycles engine offers physically based path tracing on both CPU and GPU: unlimited CPU rendering from $59.97/month on RenderStreet One, on-demand CPU from $3.00/server-hour, and GPU rendering on NVIDIA L40s at $4.49/server-hour. See the Blender render farm to get started.