I’m a bigger dude too – 6,4 about 250lbs give or take :). My advice is for general fit regarding the common apparel makers: Pearl Izumi xxl works for me (bottoms and tops). Pearl stuff is just top-notch quality and fit for me. For cold I actually wear a Marmot insulated shell, XL. The key issue for tops for me is the arm reach. Marmot and in fact Mountain Hardware seem to have extra give and length in the shoulder and arms.
Related tip: Icebreaker, maker of Merino-based clothes fit me well but the price points are really high but they seem like they will last long though. Related, related: the now-out-of-business Ibex wool clothier jerseys fit me very well and last FOREVER. AND Amazon still has some available.
Ok I forgot one other: Kuhl fits and wears well too.
Ok there’s more: Zoic shorts fit me well even though I prefer the stretchy Lycra Pearl chammy shorts for comfort and cooling.
Hope this stuff helps.
Framebreaker