Its only 5 years old, there won’t be any build up. DON"T FLUSH. If you flush, you will put various contaminants into the coolant system from using unfiltered water and even worse, flush chemicals.
Just drain and refill and don’t worry about a little residual old coolant being left behind. That old coolant is not contaminated, it’s just that its corrosion inhibitors are worn out, the new coolant will have fresh corrosion inhibitors in it and you will be good for another 5 years.
If your car were 15 years old and the coolant had never been changed, then I’d agree to a flush, but in all reality, it probably wouldn’t save the system.
If you do a drain and refill every 5 years, your system should give you 20 years of trouble free operation, though you may want to replace the thermostat and all the hoses at the 10 year drain and fill.