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Have no Di2 experience but you can change gear and brake from the tops with etap.
AXS range means I’m basically in the little ring off-road & use the big ring to get there. Unusually for SRAM, I’ve also had no issue with FD shifting so far. The FD battery is basically a big mud catcher as it sits so close to the rear wheel though
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yea for sure i use both. 50 x 11 isn't really necessary per say but i like ripping descents. particularly will use it to sprint into them or on flat sections in the middle of one. this is on a bike that does lots of big mixed surface rides, so can have steep unrelenting gravel and also loads of road. 48/31 x 11-34 maybe would be slightly more optimal but that'd mean grx fd, crank (not available in my preferred length), new pm, etc.
if you have a wide 2x system you can easily avoid shifting the big ring constantly on singletrack. especially with di2. i ride singletrack all the time with 50/34 x 11-40. singletrack i'm basically always in the small ring. 34 x 11 is plenty big on tight/tech stuff. in any case di2 fd are so good that you can shift it really most any time without a hassle.