You are correct in that speed does play a role in a backhand throw hyzering out too early from a flat flight. However; the largest determining factor is actually the fade. A disc that fades late and little flies farther than an equally fast and gliding disc does simply because the little fading disc remains horizontal maximizing glide fighting gravity longer. So the flight time is longer which automatically increases distance. You're right about mentioning weights and for sure lighter discs are easier to get farther. At 300' Discraft Z Stalker fades the least out of tweeners. That is discs that are in between mids and fairway drivers. Out of fairway drivers Innova Leopard has the least fade. For distance some speed and glide is mandatory and all current designs fade more than the Leopard. Latitude 64 River gold line has a pretty small fade and power requirement with a great glide. Innova Sidewinder was crap for years but they got better last year at least in Star plastic. It is still a touchy disc and as the name suggests it is made to flip so you could very well like it. Innova Beast doesn't flip but fades the least out of discs that are faster than the Sidewinder. If the Sidewinder flips too much and the Beast fades too much an in between disc is Roadrunner another roller.
Going light with faster discs than the Beast can help too but finding a good mold at the proper weight is difficult because currently Blizzard discs are very inconsistent. Knowing how to tune a disc could seriously help in getting a light disc to work properly for you. If you go that way a 130s Millennium Zero G Quasar could work. If it fades out too much then a 130s Wraith might be ok. Mine was flippy as hell. Before trying a Katana i'd pick one or the other out of those to get bearings on how that works for you and what you need if they don't work well enough for you.
Flat shots need running on the center line of the tee and planting each step on the center line. Anhyzer needs running from rear right to front left with the plant step hitting the ground to the left of the line you're running on. Hyzer is the mirror of that.