Yes, P90s are very, very underrated and often forgotten in my mind. Since I discovered them I am hooked. HBs and SCs also have their place and I will use them too, but to me P90s really are the best of both worlds.
I use 500k and they are most widely recommended. Some people like to exchange either tone or volume for 300k too to take the highend a bit.
I cannot speak directly for the Stockholm neck as I went with the Supermassive but I can compare that with the MQ and add what I have been told by Ben.
When you compare the MQ to the SM the SM has quite a bit more bottom end and a more modern voicing. It however does not get muddy, but it really is big on clean chords and such. The more modern voicing makes it a bit more fluid and fat, while the MQ has more of a old school bite to them. They also to me feel a bit more agressive because they are brighter. The MQ does not lack bottom end btw, so it is not that kind of bright. Both can really roar and scream, but one is more modern and fatter, bassier, the other more vintage, biting and brighter. Thing is that both can easily be made to sing too, which is really nice about P90s too.
When you factor in the SH neck that is supposed to have even more bass, hotness and agression (in that modern sense) than the SM, which is why I went for the SM. The LP I have put it in is really have and has a deep kind of bass and quite a bit of it, so I felt the SH would have been overkill for me there. Plus I like my neck PUs brighter.
Actually I am still searching for a proper home for my MQ neck. Tried it in a semihollow downsized LP, all mahagony with rosewood board, a Feline custom and currently I´m giving it a run in my Ibby S series with the IT middle and RY bridge. In the Feline I now have a Manhattan which is much nicer and sweeter for cleans in that axe and in the Ibby I will go back to the Mule that was in there...or maybe try the AM neck just for fun.
This trying has showed my that the MQ neck is brilliant rock PU, but for my taste it needs something like a les paul. In that I am 99% confident it would kill.
For what you are listing as styles I would say to go either the SH or ask to get a SM neck with the Stockholm bridge if you want to go P90. It will sound crushing, roaring and freaking alive. Like a grizzly bear on meth that just sat through a marathon of day time telly Clockwork Orange style!