There isnt a numerical deck size limit
Before we get into discussing Baby Shiny Pokemon, first things first what are Shiny Pokemon in general
Do not miss some of Scarlet & Violets standout pieces, such as Parasol Lady, Groudon SR, and Garchomp SAR
Part of a cycle that features the almost-as-broken Gaea's Cradle and somehow the hilariously unbroken Shivan Gorge, Tolarian Academy taps to make a mana for each artifact you control, which led to decks that would dump their entire hand of cheap artifacts, make a ton of mana by tapping and maybe untapping Tolarian Academy, and then use big card-draw spells like Windfall and Stroke of Genius to refill before eventually milling the opponent out with Stroke of Genius, potentially all on Turn 1
Mendicant Core, Guidelight With power equal to your artifact count, Mendicant Core, Guidelight scales from a humble 1/3 into a massive threat in treasure or clueheavy builds
The concept is reasonable: the card stock, the ink, and the number of layers are controlled in a manufacturing process so the cards should be close to the same weight within reason