Laptops, especially older ones, often have weak GPUs soldered onto the motherboard rather than a dedicated PCI graphics card. Every pixel that it has to render will add some overhead, so reducing your render resolution in the options menu should improve FPS a bit. The extra markings COULD also add a little (maybe unnoticable) overhead if your onboard GPU has little VRAM and has to constantly swap textures out.
To reduce load on the CPU, you can turn vsync on during the OGRE startup menu. It will sync FPS to your screen refresh rate and should prevent rendering 200 frames in one second and polling events for each frame (polling too much make your CPU hot and make it throttle/slow down).
Screenshots will cause FeralHeart to stop rendering frames while it's being processed and written to disc only, so just having a bunch should be a-ok.