Workbench will run from just about any bootable device, harddrive, external floppy, cd-rom etc
What you original games were coded to run on were the bog stanbard Amiga 500, ie 512kchip/512fast and KS1.3 from the internal floppy. Some original games will not run if your external drive is active >this is why some external drives have a disable switch bcuz each additional floppy device will eat up 21k of chip ram<
KS2.04 will allow some original games to boot, if you have 1meg chip and some true fast ram on your system. Usually those original games marketed as ECS or A3000 compatible.
Az