I’ve been using N565 with 140 SMK, and 147 Hornady ELD Match bullets with good results. I was originally planning on getting the N568 but I couldn’t find any. I think you’ll be happy with the performance, especially with the 156 grain.
I did, cant remember charge weight off top my head, but it was a full case. 156 eol. Topped out around 2920 from a 24" barrel. But 5 shots ranging 2870-2920 were under 2" at 200y. I wanted more speed so persued a faster higher energy powder.
I think a lot of us thought N568 was going to be a short cut version on N570 and since 570 tends to produce some of the best velocities but is very bulky so you often run out of room in the case before you hit max we were all pretty excited about the new Viht N568 but with regard to velocity 568 has kind of turned out to be a bit of a dud.