When an image needs to be scaled onto a surface the Mapping node can be used to set the scale of the image.
In Blender 2.80 this common setup looks like the screenshot attached below:
The wooden plank texture (the background plane in this image) is set to scale 3.5 in RPR to make many the plank texture look okay.
If you then set the Rendering engine to Cycles the following happens:
The texture is correctly scaled to 3.5 times it's original size and appears 3.5 times too big on the background plane.
To fix this you must use a much smaller scaling factor.
The following screen displays what 0.35 scale looks like in Cycles (to make the texture appear closer to how it did in RPR at scale 3.5).
I believe that RPR is scaling images 10x bigger than Cycles when UV Texture Mapping is required to control the texture scaling.
I hope that this bug can be fixed.
It has many issues surrounding opening scenes created in Cycles and then trying to render them in RPR.
It may also be worth noting that although all of these tests were done in the official Blender 2.80.... if you open a scene with the Texture Mapping node in Blender 2.81 Beta and try to render with RPR the renderer will do nothing stating that the Texture Node is incompatible. Blender have changed the Texture Mapping Node completely in Blender 2.81 Beta.