Solving a doubt

Context: I am a writer and want to make a map (a world map) from total zero. I was looking for a program and a good option was QGis, but i don't know if it is the best tool actually. I want to make tectonic plates, start from there and then creating the world with that.

Just downloading the program, i am looking for courses but i see mostly that are like downloading real maps and editing from there, but in my unkowing seemed like perhaps couldn't be the best program if that is the case. I am willing to learn but i need a compass right now. The story of my book is the most important but i want give my best to make a world up to the standards of the story so this is necessary. Thanks in advance for any information