Estimated points and player clashes

Hi there

I have two questions. Regarding estimated points, I thought they were a fixed number based on the previous week or split but I've noticed a number of my players points changing just hours before their first game. How are they calculated?

Also, from a tactical standpoint, is it a bad move to have two players in your starters who will play vs each other that week? For example, I have bjerg and stixxay in my starting and they vs tomorrow. However, I don't feel like my alts will do any better than a losing bjerg / stixxay.

Any help much appreciated!