Why the title says "No Pre Mine"? Isn't 20% of all block rewards goes to devs?
Yes, or rather I "think yes" (I don't remember if it's 20% but I think it is), but that's not pre-mining... that's a developer fee.
A developer fee is theoretically better for the community and investors than pre-mine since the team is going to win more in the long run if they develop the project as opposed to instantly selling their pre-mine when the value increases a little.