Most of us don't prefer ARC at all. Maybe when the advanced ARC with lossless capability comes out (but then tv apps won't likely have that as a source).
I just plug my fire sticks into hdmi ports on the back of my avrs, and as long as you have decent wifi signal, you're good to go. HDMI from avr to tv (and it will be for video unless for some crazy reason you want to use tv speakers).
ps Which input on the tv as long as its hdmi wouldn't matter (some avrs/tvs have restricted hdmi ports for ARC, tho)