If you want a printer that has everythibg for you, that is plug-and-play, get the pre-assembled Prusa. It's one of the more expensive printers but of very high quality.
The Creality Ender 3 is another legend in the scene. It's like 1/3rd the price of a Prusa. Problem, it comes worse and it's up to you how good the prints are. A prusa is also able to perform better, but you will need to get the Ender to match the prusa first.
Always get the bed as flst as you can. It says that it can correct wobble up to 2mm but you don't have good tolerances that way.
As a Nozzle, you'll probably want as fine as you can because that way you up the tolerances.
Ideas, there is this channel called MDpuzzles that has some designs for lesrning I believe.
Software, there is a ton you could use. SolidEdge, SolidWorks, Blender, Fusion360, AutoCAD, LibreCAD, FreeCAD and that's just what I can tell on top if my head.
The problem is, if you don't work in any kind of Woodworking or Metalworking, you'll likely have no concept of 3 dimensional Drawings and will need to start from scratch. Aparently, higher schools and colleges have CAD as a course. I wouldn't know, never been to a higher school, only Furniture school, where we were taught AutoCAD (and NC Hops, but whatever). I perfonally have bought an AutoCAD license because I use it commercially, but you get the full version for free as a student. Same for many others.
If you want to get the basics, buy shengshou 7x7s or other cheap big cubes and a filler material like Epoxy Putty, sandpaper, needle files, cutter/Xacto knives and super glue. Then start designing bandaging extensions and make your own cuboids. Get's you in the process. Look as JRs Videos about TwistyTex extensions and learn by doing your oen research/dimensions.