i was wondering since i take miralax and have fluffy soft poops now. will i have more build up of bad stuff on the walls of my intestines? i would think regular poops that are bulky would clean you out better? also will having soft poops make my anus even tighter over time or will it be more loose?

No to the plaques problem. Your poop is normally pretty loose until it reaches the very end of the colon, where water is removed until it becomes solid-ish. So having soft poop isn't going to change anything. In fact, its probably better for your colon because the stool will move through your intestines faster. Its no good to have stuff slogging around up there longer than it needs to be.
Yes to the bulk in the stool. My CRS wants me to add bulk to make my poop larger to act as a dilator for the rectum. He said you want soft and large. Your stool should be soft, but not loose. It should still have some form when its in the toilet. If it mixes with the toilet water before flushing, its diarrhea and that's bad for the fissure.
A normal stool is the size and shape of a bananna, and floats in the middle of the toilet water, neither sinking or floating, according to Traditional Chinese Medicine, where poop is a major diagnostic tool. But most of us are aiming for slightly softer than that, I think, while we heal.

Actually delasama the intake of fibre is what keeps the colon healthy and clean, I had always take fibre all my life, but at the same time I always had soft stools and very lose stoles.
In my first colonoscopy my doctor told me that my colon was so clean it shines than means that fibre is good for you and your instestine while constipation can be your colon worst enemy.
Be happy with your "fluffy soft poops "

Thankyou two for the great info!

So coconut, there IS an intermediary poop which neither sinks or floats. That's all I wanted to know. You are definitely a master poop analyst :)