You can not use Proxy card to participate in any level of Magic: The Gathering competition with any Rules Enforcement Level, because it's not an official product
The biggest downside is that its frail to artifact removal, the Vandalblasts of this world
P/T Number 226 Language English Legal Formats Brawl, Commander, Competitive Brawl, Historic, Legacy, Modern, Pioneer, Timeless, Vintage Not Legal Formats Alchemy, Pauper, Standard Rulings (5/12/2023) Sigarda lets you look at the top card of your library whenever you want (with one restrictionsee below), even if you don't have priority
(2025-06-06) The mana value of a spell with tiered is determined only by its mana cost (in the upper right corner of the card)
It's hard to be upset with a removal spell you can cast twice, and this one can also just be used to draw a card in a pinch