Though the 1.25 drain should able to handle the flow, I like to use larger pipe for overflow lines to the sump, just in case some kind of debris gets caught up in a drain line. It's amazing what a few snails and some plant parts can do to stop up a drain, and create a tank overflow to the floor. For 1" or 1.25 PVC from pump, I like at least 1.5" drain, or even better 2" to sump.
Especially if the overflow is one of those crazy twisted PVC types.
I also like using ball or gate valves only on pump outflow, flow from centrifugal pumps are easily throttled back, where as centrifugal pumps can easily be burned out if flow to them, is choked.