Traditionally I have run mostly homebrew adventures. I’ve used encounters taken from commercial adventures every once in a while. The Dragonlance campaign I’m running is the first I’ve really tried to run a module straight.
My players aren’t always going along with that idea but that’s ok. I’ve also added some content because I wanted a special event for the character with divine powers. I plan to do the same for the knight. Due to this I created Dulsi’s Dragonlance Addendum on DMs Guild.
For Spelljammer I found the process less satisfying. I had to tweak many individual encounters to match what I wanted. So running it requires looking at the adventure and looking my notes for things to override.
I have never used a campaign module as written. I don’t know that I could. I started with homebrew adventures, and that’s what my mind adapted to.
I get an idea of the adventure module in my head as I read it, and then I fill in the idea by myself. I often think over, adapt, expand and rewrite aspects of the idea, making it something I feel I could portray to my players. Then I use the original adventure as reference to fill in the gaps during gameplay. The end result is my version of the adventure, which is like the same image drawn by a different artist: recognisable, but different in obvious ways.