You'll be fine with 5w.
You'll definitely feel the difference of 10w also, I'de even say too much, but it's preference.
7w is a noticeable difference, and I like it, but I wouldn't want to go to 10w.
At 200 lbs you shouldn't be more than 225 lbs suited. If you jump from 5w to 10w with the spring change it adds another variable.
Without experience with different fork oils you won't be able to tell what caused the change in how the forks feel.
Stick with the 5w, you can always change the oil. I'de go to 7w next if you do, as said, you'll feel the change.
Body weight doesn't account for a need of thicker oil, just heavier springs. Thicker oil can be a bandaid for a heavy guy needing firmer springs, but won't do the job of them.
Make sure the front and rear sag is set properly and you'll be fine.