These achievements do track over multiple worlds so you don't have to build all 1000 foundations in one world. For the Builder achievements, I would build an extension off of the back of your Raft and build a platform of foundations in 10x10 chunks once you have a lot of excess wood and plastic. Building 100 foundations and then destroying them before building the next 100 foundations will reduce the amount of lag in your world that can come with having large builds.