For a Win 10 install, and a 64GB drive, you should have around 30GB usable space left.
But for your main question, just choose where you want things. But as said, applications don't really take up much space. Even something large like MS Office Pro only uses about 3GB of drive space.
Same with image editing applications.
My Lightroom and Paintshop Pro applications only use up about 2GB combined.
The folder with the pictures takes about 50GB. That folder lives on a different drive.