Nice dude. The Sigma+FF is a heavy setup, but sounds awesome. The 24-105 is a great oudoor lens, but the 2.8 lens will be more versatile if you want to use for indoor stuff.

I use the Lowepro Adventura TLZ 20 II and it's very snugged for A6400 and 18-135.

I tour with an Sony A6400 and 18-135. And I use a peak design capture clip. If it's snowing or powder out, I just put a drawstring bag over it and cinch it down. I've tomahawk down soft couloirs with...