I was Nikon full frame guy for 35years. Then one day, I got tired of my 20 plus kg bag (not all the stuff even in!)and I switched to mirrorless system.
Today I shoot Olympus OM-D EM 1 MarkII together with pro series lenses. In my pack bag I normally carry three bodies, 4.o- 300mmPro (600mm eq), 2.8- 40-150mm Pro (80-300mm eq) 2.8- 12-40mm Pro (24-80mm eq), 2.8- 7-14 mm Pro (14-28mm eq), 2.8- 60mm (120mm eq) macro, 1.8- 45mm (90mm eq). All that with some accessories and carbon tripod is only around 7 kg!
I just love the Olympus system and I am very happy with the picture quality.