The problem inherent in going all in on a top QB - aside from the obvious history of flops with so many of them - is the quality of the O as it now exists and with the inept coaching of Rico and his staff. Put any of the elite college QBs into that mess and it's likely to resemble Peterman and the Chargers week after week than Dak Prescott's rookie year.
There is an old adage that says you build a team from front to back, inside to outside. With that in mind, I would replace the O staff first of all then spend the picks on the O line and both a top, field-stretching receiver and a running back. Until the O is improved talent-wise, no QB, elite or otherwise, will make a damned bit of difference, and particularly a rookie. The only way the Bills should pick a QB in the first two rounds is if one of the top 3 QBs not named Mayfield happens to fall to them for some unknown reason. Otherwise, use this draft to "set the table" for one next year or the year after.
You see no red flags with a 5' 11'' QB who exhibits some Ryan Leaf-like characteristics?