I have not messed with a wet brine for awhile. Meathead at amazingribs.com told me it doesn't work but I haven't personally tried. I usually cross cut the top and season it 1-2 hours before it goes on if I have that much time. Then leave it sit on the counter for 30 or so minutes of that time to start bringing the temp up. Don't know if it is true or not but it seems like that osmosis from the salt really kicks in during that time on the counter.
Since it is the offseason we can start a fight on the board. Meathead also says fat side up doesn't matter. Says the fat rendering does not change the composition of the meat at all and therefore does not affect the finished product. I think he has a point and is probably right but I also don't tempt the Meat Gods and roll fat side down.
I don't brine pork, just dry rub and rest like you say. I've never tried it to be honest (that I recall) but I get results I'm happy with, without the extra prep work. I do wet brine chicken every time, then use a light-flavor rub after rinsing and drying it. I just don't trust chicken.
Fat cap: with my setup resting on a pan+grate in the smoker, I'm pretty protected from the heat by the tray and grate to begin with. However I still always put fat cap down because:
1) I'm not sure if rub really does much through even a light or trimmed fat cap anyway (I still put a little on that side)
2) I want to be sure the bare meat is as exposed as possible to the airflow of smoke
3) when doing a pork butt, the bottom (fat) sometimes sticks a little bit to my butcher paper -- if it's mostly fat I don't care and it's maybe 5% easier to yank out the meat and pitch out the fat layer
4) I nearly always inject marinade to be 100% certain I have all the liquid I need to end up with a juicy result in the end (plus some savory flavor)
5) there's so much marbling in a typical pork butt in particular, worrying about how the fat cap interacts seems redundant
I probably agree with Meathead that it's a quibble that largely doesn't matter at all. You can get a great result putting the meat in any orientation. It's several other variables that have much greater impact that determine success.