Qcad is fine. I did drafting/autocad in High School (2002) and it wasn’t too bad.
I tried sketchup and it is not great for 2D. For 3D I didn’t like it as much either, I felt like you have to use the mouse a lot more. I had a ton of trouble just subtracting a volume in sketchup (creating a window in an extruded floor plan)
I use SweetHome3D to arrange furniture before I move into a new place and I know that homebuilders and realtors use it professionally. I don't know to what extent it will be useful for a professional architect.
LibreCAD is probably the best free one and Autodesk has fusion 360(free for personal use I believe) , but honestly most people prefer a pencil and paper at first.
Note: it doesn’t need 3D capabilities, just ability to create 2D blueprints.