When it comes to "Super Pershing" vs "King Tiger" then its more about "Who shots and hits first?".
The King Tiger had 150mm frontal armour.
The Super Pershing had 140mm front armour on the upper part and i think 177mm at the lower part(2x +38mm steel plate)
(It was an upgraded Version of the normal Pershing.Super Pershing had the 102mm front armour of the normal Pershing + an additional Steelplate of 38mm. 102mm + 38mm = 140mm)
Both guns were very very powerfull.
The super Pershings main gun the T15E1 90mm L/73 had a Barrel lenght of 6570mm(90mm * 73).King Tiger had 6250mm.Only the Jagdtigers 128mm L/55 had a longer gun with a Barrel lenght of 7040mm(128mm * 55).
Only 1 of the super Pershings were ever used in WW2.Would be super rare.
Relic could maybe add the super Pershing as a limited 1 time call in similar to the Tiger Ace.
This pic Shows the "super Pershing" compared to the normal Pershing.That Thing Looks like fun.You can see the 38mm extra steelplate on the super Pershings front in the pic.
As Long as my German OKW have the Jagdtiger with 250mm armour and the 128mm Pak 44 i see no Problems with a super Pershing.