The nature of night fighter tactics creates a force that is bound to be numerically smaller than a day fighter one. Much of the infrastructure is ground based, witness the Kammhuber Line and the associated ground radars. The airborne Lichtenstein taking over only for the final interception. The system was clunky and easily overwhelmed by using the single bomber stream to do so. Thereafter it was measure and countermeasure by both sides, even resorting to day fighters (Wilde Sau) and upward firing cannon in the night fighters (Schrage Musik). But numbers involved were always less than the daytime interceptions. One was a precise choreography, the other a swarm. To infer it was an insignificant drain on Luftwaffe resources (which also provided the flak batteries of course) is misleading.
Would medium bombers have better disrupted Germany's ability to conduct the war rather than BC's heavies? I can't see how. The Luftwaffe had only medium bombers and the answer to them in the East was to withdraw the targets outside of their radius of action. I've no doubt that if the RAF had switched to medium bombers the targets would have been moved accordingly. It was the ability to follow them that gave the Allies the upper hand in the bombing offensive. In the end we would have had an enormous fleet of twin engine bombers and a paucity of targets for them to strike.