This is a never ending question with many facets to it from: Anything will work to never put toilet paper down into your black tank and put it in the trash(yes even with poop on it).
So you will hear from all ends of the spectrum.
https://www.rvrepairclub.com/video/selecting-the-best-toilet-paper-for-your-rvs-waste-system-007915/ <– that is only a preview of the full video BUT the final conclusion of the test was this: Get toilet paper that is RV rated NOT NECESSARILY septic safe, Thetford toilet paper seemed to be the winner.
Here is link to what I use: https://amzn.to/2BTg8Ar
It is important to keep in mind you want something that will dissolve easily and ALWAYS use more water flushed into the black tank that you think you need to. More water in there IS ALWAYS BETTER.