Cokin P and Formatt Hitech filters

Hello, I would like to add another filter thread. ;)

I want to buy a filter system for my 80d and 18-135 STM. I can't justify the cost of good 100mm x 100mm filters so I have been looking at the Cokin P system with a 10 stop nuances filter and circular polariser.
The older cokin filters have a bad purple/magenta colour cast and the nuances series is very expensive in the Netherlands so I have been looking at the Formatt Hitech filters.
Now my question is: Are the 85mm filters compatible with the cokin P system because i have been reading
a couple of conflicting stories with some saying they work perfectly and some saying they dont really work.

The second question: What do you think about the nuances series.

I hope You have a good day!!