I'm buying a Keycool 87, also, with PBT keycaps. Yes, you can replace all the keycaps. Those from eBay seller WASDkeyboards (also at
www.wasdkeyboards.com) will be the same height as the stock keycaps on the Keycool. That novelty LoD keycap from eBay seller key-pop (also at
www.key-pop.net) will be slightly lower profile, but not radically so.
Also, Welcome to Geekhack!