Umm the 37mm wasnt an at gun. Tony Williams has stated this before. It sertainly strafed light armored and soft vehicles butit was used a2a to mostly AFAIK.
Even the 37mm of the stuka with its tungsten core had a hard time killing tanks. Thats like saying the Mk 108 was only to kill bombers. Its just not correct.
The yak 9u had was better above 4000 meters and was faster at those alts. Thats one of the reasons yaks 9us were flying over berlin and yak 3s we following the front line.
IMHO the yak 9u (except for post war yaks) was the best. I dont think we will get a Yak 9 / Yak 3 because WBS has umm.
Some sources refer to it as just "Tyazhely" (heavy) and the k was "Krupnokaliberny"
* The first refinement of the Yak-9 was the "Yak-9T", where "T" stood for "Tyazhelowooruzheny / Heavily Armed", fitted with an NS-37 37 millimeter cannon firing through the propeller spinner instead of the ShVAK 20 millimeter cannon. The variant went through evaluation in early 1943 and was in field service by the spring of that year. It proved very popular, with 2,748 built.
To accommodate the cannon, the cockpit was moved 40 centimeters (1.3 feet) towards the rear. While some sources claim that the Yak-9T was designed as a close-support aircraft, it appears that the fit of the NS-37 cannon was mainly to correct the inadequate firepower that had dogged the Yak-series fighters, and the Yak-9T was primarily used for air combat. The USSR had a better machine for close support, the heavily armored Ilyushin Il-2 Shturmovik.
I am sure Tony has better sources then I do.
Start a thread in the A $ V forum titled "NS-37 - 37 millimeter cannon" I am sure Tony will be along to answer the question.