I've recently started up a 1.18 SP Minecraft World, and I've always wondered about this. How do people plan out their building designs? I always end up with some generic box home, because I don't plan anything. I wanted to build something way more interesting either I'm too uncreative or there is a way to plan things out better.
One thing I really enjoyed years ago was playing on the Mithrintia server (
Home | Mithrintia) which is now defunct. They had an extremely active creative server that, when joining, limited your ability to place things to a small plot (50x50 iirc) that you needed to build something "decent" on before you were allowed access to modify a larger plot. You could fly around and see other people's (really amazing) stuff, but could only work in your little area of the world.
This was good not only because it helped "force" new builders to add things like detail, depth etc in a very manageable area, but it also birthed literally thousands of mini-builds that you could peruse very quickly to get ideas. It's tempting to get enamored with mega-builds that are created by teams of builders who often have expertise in powerful tools, existing sources to draw from and weeks of time to implement it, but then once you try to build your own mega-build by starting big you end up with something that's flat, boring, repetitive and needs to be redone from the ground up before it's worth showing off.
So, anyway, what I'd recommend is finding a creative builder server, I have no idea what's out there for that. I also recommend starting small and trying to figure out how to add detail. If you want to build something really big, figure out the basic pieces first before trying to plan out the megabuild.
The other thing I'd recommend, which is true of art in general, is to understand what the medium is suitable for before deciding what to build. A common noob trap people run into is wanting to build stuff that can't be built with 1 meter blocks unless the scale of the build is so massive you can build clean curves with it. At some point it's like, just learn how to use Maya or Blender to create your giant statue instead of placing things one block at a time.