Any aircraft can go VFR.
Not all aircraft (or pilots) can fly IFR
above 18,000 feet, all aircraft must be on IFR flightplan
all commercial flights are IFR, foremost for safety purposes,
even if they do not climb to or past 18,000 feet, (certain portions of the flight may be visual, like the approach if weather is good)
turboprops are most efficient between 20,000 and 28,000 while jets are most efficient between 24,000 and 40,000 feet. That's why most tprops and jets fly high and IFR.
also, there is a speed limit of 250 knots below 10,000 feet, regardless of IFR or VFR for most aircraft. (military aircraft can get exemption)