primegrid.com - what's the difference

[Max Dettweiler]

http://primegrid.com/stats_pps_llr.php

they use k < 1200, n > 500000 AFAIK

how nplb and pg check to not use the same range and the same k&n?

Here's the difference: NPLB is searching numbers of the form k*2^n-1, and PrimeGrid's PPS project is searching number of the form k*2^n+1. They may look similar on the outside, but actually they are completely different numbers.

Now, of course, these two types of numbers behave very similarly when it comes to sieving and testing them, but they are still different enough that PrimeGrid is definitely not doing the same work NPLB is.