For softwares, I use a bunch depending on the need.
Quick rough sketches are done in Tinkercad. (Free). You can do ALOT with this super basic program
More technical parts with detail are done with Fusion360 (Free hobbyist license), and it even integrates with Tinkercad so you can start in Tinkercad, and refine in Fusion360. Great for functional items.
Organic shapes I prefer Blender. I designed my buddys scuba boat in Blender, was the only way I could figure out the complex curves in the hull. Great for minis and other sculpture items.
Its good to note, all three programs are free / free for hobby use, they all have big communities and lots of good tutorials on Youtube as well.