The (Project Horizon) engine itself can be run on any amiga (even on an unexpanded one). That means that if you will make a new game with it you have to use maximum that amount of gfx/sfx/etc..
The game QUEST needs ECS and at least 1.5Mb Chip ram! That means if you have an Amiga 500 (probably 500+) with an ECS chip with 1.5Mb chip ram then yes you can play with it! If you have an OCS (standard A500) that means that you are strucked at maximum 1Mb Chip ram! That is the maximum amount of chip ram an OCS machine can handle.
Simply the game uses a lot of gfx, that is why it eats 1,5MB of chip-ram.