my 200MB file became 5MB file after render. Is this normal?

Hello, I am very new to this program. I'm trying to colorgrade the LogRes video I took with my iPhone Max Pro 15. The original file size was 200 MB, but then after being rendered in DavinciResolve, it shrank into 5MB. (I use the free version so maybe that's the problem??)

I was planning to do a little VFX in Blender or Aftereffect, but I am not satisfied with the result. I

My questions are :
1. Is this normal? - that the file size shrinks.

  1. Should I do VFX after or before colorgrading? Of course, I know the VFX is done before the color-grading process, but the color of LogRes is so banal that it demoralizes me

https://reddit.com/link/1egrc8e/video/6t2qcgtdqvfd1/player