From my research I've found that all of the larger non-OEM tanks have issues with the highest setting of the high flow nozzles. You can click one down from max and not have an issue (again from my research). I've also read that some folks have 0 issue with the high flow, and some do, meanwhile others report having no issue at certain stations, and issues at other.
Miles to empty won't be accurate until the tank gets low enough towards the "max" setting. You can use alfaOBD to adjust the tank size, but the max size (194 liter I believe, ~51 gal since the largest OEM tank is 50 gal) is lower than the size of the S&B/Titan tank. So the MTE will be accurate once the tank dips below that. Same goes for the fuel tank gauge. It will always show full until it dips below where the lift pump "bobber" is.
These issues appear to be across the board, for any aftermarket tank larger than OEM, so it wasn't something I mentioned but it's good to note.
For me, it's not even a question. My MTE won't be accurate until I've dipped below ~50 gal. Even still, that should give me an accurate reading of roughly 450 miles, which is more than adequate.