Whichever program and/or game bangs the classic hardware needs uae which emulates the chipsets (gfx and sound). There are some compatible games (mid to late 90s) though and even CIA timing can be overridden (battleduel comes to my mind). I run adfs (mostly for games that don't have a slave, that is) via context menu with "Run in A1200" or "Run in A500". For slaves I run the games via iGame (compatible 68k app) and UAE wrapper. So, the slaves are running perfectly seamlessly. About the the web browsing OWB handles both YT and Facebook nicely though you must understand that a G4 is already a very old cpu with limited speed compared to a Core2Duo and upwards which can handle the web pretty nicely. However on my G4 1.6Ghz both YT and Facebook run ok. On the G5 2.5 I can even run 720p YT videos.