THat's quite a meaty camera/lens combination! I have a friend that shoots with a Nikon 850 and he swears its like shooting medium format. I use a Canon 5D4 myself, but I am looking at going mirrorless and picking up the Canon R5 - they are supposedly going to be releasing a 90MP version for landscape/studio photographers later this year.
I like the LowePro Flipside because the opening to the bag is on the part that is next to your back. So you can lay the bag down on the ground, mud, whatever, zip it open to access everything, but when you put it back on again the clean side will be against you, so your your jersey doesn't get dirty. It is a well padded bag and the 500 series is big enough so that I ccan carry my DSLR, a 70-200 f2.8, a 17-40 f4, three hefty Zeiss primes (21, 35 and 50) as well as the usual other accoutrements one needs. In a side pocket, secured with straps, i have my tripod, a fairly lightweigh carbon fibe Gitzo Traveller. It makes for a heavy pack but 've ridden as much as 60 miles with it - although usually mu rides are more like 20-30 miles.