[electricron]

To determine if the trains will be too slow on the 3C proposed rail corridor, one must first determine what the bread and butter, make or break, business is?
Is it (A) Columbus to Cleveland, and Columbus to Cincinnati, or (B) Cleveland to Cincinnati? It is important to make that designation, because miles travel is a major factor in determining elapse time and average speeds the trains need.

Again, I am going to suggest an elapse time of 3 hours or less is required for trains to compete with cars and planes. So milage is important.
The highway distances between Cleveland and Columbus is 145 miles, and between Columbus and Cincinnati is 107 miles. Therefore, it is 252 miles between Cleveland and Cincinnatil

3 hours elapse time goal math:
145/3 = 48.33 mph average
107/3 = 35.67 mph average
252/3 = 84 mph average.

To average 35.67 mph, existing 79 mph trains over Class 4 tracks can easily be achieved with minimum upgrades to the rail line. The major cost will be limited to buying new rolling stock and subsidizing the train's losses. That is assuming the tracks are already meeting Class 4 conditions, and not Class 3.
To average 48.33 mph, existing 79 mph trains over Class 4 tracks is at the limit, more than a few upgrades to the existing rail line concentrating on eliminating slowing down of the trains in congested freight train areas, like building a few flyovers would most likely be needed.
To average 84 mph average, a major reconstruction of the rail line would be needed eliminating all at grade crossings much like the Class 7 NEC tracks with trains going 125 mph maximum speeds or upgrading the rail corridor to the Lincoln Service in Illinois Class 6 tracks as a minimum upgrade with 110 mph maximum speeds.

I do not think 186 mph (300 km/h) maximum speed trains will be needed Cleveland to Cincinnati to achieve less than 3 hours elapse times. Never-the-less, major upgrades all along the existing rail corridor will be needed.