Hi Patrick, and welcome. There is alot to address on this subject, so here goes ...
On the clothing subject, most members here use a similar system. A base layer with a windshell over it, and then adding layers to accomodate given conditions. The exact pieces depend very much on individual needs and preferences. For daytime conditions between 10*F-30*F I personally wear an Icebreaker 260 zip-t, powerstretch facemask, and a MYOG hooded windshirt in Epic(comparable to Wild Things hooded windshirt). I believe a hooded shell is crucial in cold, windy conditions, and I like the facemask because I haven't been able to purchase or build a hood that seals as well around my head. To these pieces I add a silkweight tshirt under the zip-t if I know it's going to be on the colder side. I also carry a light microfleece windstopper vest I can wear over everything. For the coldest days, I will sometimes wear a light fleece pullover over the zip-t. For reference, I'm 6'1" 155 lbs and get cold pretty easily.
For a warm coat, my choice would be a Feathered Friends Hooded Helios. 9 ounces of 850+ down in a sub 20 ounce coat is very efficient from a fill weight:total weight standpoint, and at $289 it's less expensive than comparable coats. There is also a choice of shell fabrics; my choice would be Epic. I really like the performance of Epic for clothing shells in winter, though I wouldn't choose it for a sleeping bag shell or bivy sack because of other members' poor experiences in this circumstance. On a down coat however, Epic should mitigate the need to wear a shell on top for moisture protection, at least in winter.
One thing you didn't mention is footwear/lower extremities, but I'll touch on it. For inexperienced winter travellers it's worth the price of subscription to access the articles on winter footwear alone. There is a wealth of info there, and a number of solutions for dealing with the problems of multi-day winter trips as regards footwear/footcare, as well as systems and strategies for dealing with various conditions. Winter overnights present some big problems regarding footwear. Drying shoes/boots overnight outside is problematic, and keeping feet dry and warm both while moving and stopped is difficult as well. Feet become wet and cold more easily in winter, so drying/warming and blister prevention become more important. Get some down booties for camp (I like the Feathered Friends modular booties) and consider VB socks, which a number of members here have found success with.
For the lower extremities, you're going to need insulated pants. As Dr. Nisley has explained in numerous posts, it will be nearly impossible to stay warm in camp for your expected conditions wearing only an insulated coat. Insulated clothing covering your entire body is necessary in places like the Whites in winter. Insulated booties and pants will also help you stretch your sleeping bag's capabilities.
For a sleeping bag, there are a number of variables. You can get away with a lighter bag rated 15*F-30*F at lower elevations in NE, but the big peaks will require something warmer, even using insulated clothing. I use a WM Antelope SMF; it's rated to 5*F standard, mine has 3 oz. overfill, so 31 oz. total, as compared to the typical 20 oz. fill of 15*F bags. Nearly 8 inches of loft by my measurement, and it would be the lightest bag I would take for a NE winter trip above treeline.
Lots to think about, and you've found IMO the richest source in the world for the knowledge you seek. Tell us a little more Patrick about your build and metabolism, and what gear/clothing you're currently using. And prepare to be overwhelmed; there is alot of great gear out there, and even more opinions about it!