Yes, a pyramid tent is my preferred option for miserable conditions during the arctic summer. However it takes some experience to set it up in unrelenting rain and wind in conjunction with exposed locale -- and with winds strong enough to cause hypothermia as well as strong enough to destroy UL shelters that are not pitched well.
Chris, I absoultely swear by that style of tent, given my own ultralight style (multipurpose, sharing, spartan)
"(1)Would you take a bivy in addition to the tent/tarp?"
No -- I gave up on bivy sacks two decades ago; however, did use them for many years. Eventually discovered they did very little but add weight to my pack as they got wet. Prefer synthetic bags and foam pads alone. But I am very aware that this is a personal issue and there are likely people reading these very contentious words of mine who started using bivy sacks 2 decades ago and would never consider going without one.
"(2)How would you deal with camping on really wet ground, eg some of the artic bogs?" Look for a better spot! But suppose it's rainy and the ground is all wet. Well I spread my rain gear down on the ground inside facing up. Then put my dry bag down and then my foam pad and pack. Generally I build a little island of dryness and sleep on top of that. It's amzing how adept you get!
I prefer the philosophy of building dryness in a wet world to trying to keep the wet world out of a dry tent.
Climbing into a dry tent with wet clothes gets the tent wet. Climbing under the mid and onto the wet ground with muddy boots and wet clothes is no big deal. It feels great!
then I strip and build my island and sleep warm, dry , and happy.