i no im responding late but since no one said it i will any version of mugen can be set to full screen and lines of resolution changed turned to high res or 3 lvls of non high res you can do it manualy or with a tool called the mugen configurator there just options in the system def file/cfg file .go with bilinier filtering on double res thats 2 i believe .640x480 or whatever .screen stretch and software mode will make it full screen
aditionaly you can change the numer of chracter slots and there small pic sizes the same ways pick a sceen pack you like not one you settle for