Not going by PSA pop reports, just how many copies in any conditon and not including trophy cards.
My guess is WB creator pack promo, would be around 5000 or so copies.
Another possible guess would be gold star pikachu. And if we maybe include variations then these come to mind reverse holo skyridge, non holo worlds collection pikachu, red cheeks 1st ed base.
I completely forgot they had english art academy cards. I have the japanese one with pikachu holding an umbrella in the rain burned into my mind when i think art academy.
But for just the English Pikachus: same answer, since I’m still missing two English Art Academy cards as well as a grey 1st edition Red Cheeks Base Set Pikachu. But after that probably the Inverted and No Stamp WB Pikachus, since those were one of the last English Pikachu cards I added to my collection.
These two videos of TCA Gaming are also all I personally know about them: