The only visual difference between a 1st Edition card and a plain shadowless card is the "Edition 1" stamp on the lower left of the artwork
Even with stiff competition, there's no doubt that 151 deserves to be called the Scarlet & Violet era's best set, and one that will be a legendary part of the TCG's rich history
Gold Stars seem to be about 1 in 3 boxes, the Ace Spec cards from Plasma Storm and Plasma Blast are about 1.5 per box or 3 in 2 boxes, the Alph Lithograph cards from Unleashed, Undaunted and Triumphant are about 1 in 6 boxes on average
If you have a card you want to grade and there are a lot of them listed on ebay, try to find a card in a similar condition to yours
Also just a solid game-ender
This is often called "forcing the 7th prize," meaning you make them take more KOs than they need to win