Corner rounding is commonly referenced around 1/8 inch (roughly 3 mm, sometimes listed closer to 3.5 mm depending on the spec source)
At $19.99, it's priced aggressively for what you're getting, especially considering those exclusive cards will likely end up commanding absolutely blasphemous prices on the secondary market
One of the best Jund cards in sacrifice-based decks, Korvold grows fairly large and draws you many cards, and its good enough to see Commander and 1v1 Constructed play in Jund decks
It pairs well with other cards that want you to send artifacts to your graveyard, like Marionette Master and Myr Retriever, and the ample self-mill found in these colors like Grisly Salvage
A Play Area : You need a flat surface to lay out your cards and keep track of the game, the Lorcana Starter Decks come with a paper playmat to get you started