It is always recommended to set your PC or Laptop to match the native resolution that is supported by your Optoma projector.
For Optoma projectors that are SVGA, use resolution 800x600.
For Optoma projectors that are XGA, use resolution 1024x768.
For Optoma projectors that are Full HD, use resolution 1920x1080.
For Optoma projectors that are 4K/UHD, use 3840x2160.
For a full list of other compatible resolutions for your specific model projector, refer to your Optoma projector user manual.