While it is more convenient to change the DNS setting in the router, it is not a requirement. Changing the DNS setting in the computer(s) runing the browsers is equally effective when using PiHole to block ads.
It is the same type. There is very little on the board additional to that chip. You can easily find the data sheet for the chip and all the pertinent info that isn't obvious from physical examination of the board can be had from it.