When I first started using Pyrocat HD about 20 years ago I found I got excellent results with 35mm HP5 in1+1+100, at a time of 15 minutes for film exposed at 200 in sunny conditions. This time seemed a bit long, so I tried the 2+2+100 solution. This brought the time down to 10 minutes. But it also resulted in a noticable increase in grain. I quite liked a bit of grain at the time and was also developing 35mm Hp5 in Rodinal. The grain from Pyrocat 2+2+100 was about the same as you get from Rodinal. This was definitely noticable in a normal sized print from a 35mm negative, but it didn't show up in a normal sized print from a 5x4 negative. So I standardised on the 2+2 +100 for my 5x4 negatives which I was developing at the time in the dark in an open tray. So shorter development times were quite handy. And Istopped using Rodinal because I found Pyrocat to be a much better developer.
Eventually I stopped using Pyrocat when I could no longer get the raw chemicals easily. and switched to ID11 and Perceptol at 1+3. Ironically, this put me back to long development times. But I really like the results...
Alan