Internal Resolution You can select x1/x2.
EPSXE FULL SCREEN NOT CENTERED SOFTWARE
Use the software renderer only in very old devices (for example with GPU Adreno 200 such as Dell Streak 5'). In general you should choose the Hardware renderer (faster and smoother graphics), FXAA is more CPU/GPU demanding but you will get smoother images, and the OpenGL Plugin is the smoothest but compatibility is limited. Video Renderer You can select Hardware, FXAA, software renderer or OpenGL Plugin. VR Modes Support for different modes using google cardboard. You can remove the top/bottom black bands in the PAL games, getting more bigger image - which is stretched, but it can break some games (like Alundra 2 videos and loading screens). Top/bottoms black bands Top/bottoms black bands. Colors will be better in 32bits in MDEC videos. Screen color Depth You can choose 16/32 bit colors. Screen ratio You can choose stretched to full screen, 4:3 real PSX ratio, or widescreen mode. Screen orientation You can choose landscape, portrait, or reverse landscape screen orientation. It is not supported in some old devices, but it will improve performance in Adreno GPUs. Plugin Texture Mode You can select enable/disable. It reduces the rendering size, important in devices with low fill ratio as Ouya or Nexus 10. Plugin Reduce Internal Resolution You can select full resolution/480p/600p. It will improve the 3D preccision (known as gte accuracy hack in PC), but it will require a lot of memory and and fast CPU. Plugin Subpixel Precision You can enable/disable.
EPSXE FULL SCREEN NOT CENTERED DOWNLOAD
In the top/right coreder there is a button to download the lastest plugin version. You have to choose video renderer=opengl. GPU Plugin (read more below) Select a external gpu plugin to use. Disabling this option to improve accuracy. Threading mode is recommend in CPU 1.5ghz or less (but dual/quad core is required).
HW/SW Threading mode You can enable/disable the threading mode. It will improve the graphics in 2D games, with 2xsai and other filters. Video Filtering 2D You can enable/disable the 2D filtering in the hw renderer. By default the graphics will be filtered, but if you prefer graphics more similar to real PSX you can disable it. Video Filtering You can enable/disable the filtering in the hw renderer (not supported on software renderer and the opengl plugin include its own filtering options). x1 is more accurate, x2 smoother graphics, but a fast CPU is required.
x1 is PS1 resolution, x2 increase the resolution.