I had no issue with plugging in my grow of 3 pots. The initial hose from the reservoir outside the growdrobe was ~3/8", necked down to the standard ~1/4" inside the growdrobe. I did not use the standard autopot filters though, I used a pleated household filter element mounted inside the reservoir. I also used no cleaning agent during the grow. I had no issues with float valve function during the grow. Good filtration is your friend.
Larger hose will make zero difference to plugging or leaking at the float valve - absent plugging in the hose itself, nothing at the valve will be changed by the size of the initial feed hose, at least not in a home grow of 3-4 pots. With a much larger operation, flow could be limited to less than needed by friction, but flow rates in a 3-4 pot grow are too low for frictional losses in feed lines to be an issue.
Mounting the reservoir higher will increase water pressure but that is more likely to increase the chance of flooding than decrease it. The amount of sealing force provided by the float valve which stops flow from the reservoir is fixed by the size of the floats which close the valve. The higher the input water pressure, the more likely that this limited sealing force will be overcome and flooding result.
Bottom line in my experience with a 3 xl pot setup is that with good filtration, there is no need for or advantage in feed hose larger than the standard ~1/4" stuff. The chance of flooding will be determined by how clean the valves stay, and your best control of that is good filtration. If you use nutes or additives which can gel or precipitate after fine filtration, your mileage may vary...