60 Card decks in standard. You build, you use, you play. Simple right? Adding the cards up, 58/60, 59/60, and then 60/60 alright here we go.
I can tell you this is, only the standard minimum card needed to launch a match.
Have you ever noticed your, soon to be defeated opponent's deck of cards are thicker than your standard 60/60 before the draw? I have and before recently, I have feared and cowered before the mighty decks. 120 cards in a deck to my measly 60, outrageous I tell you! Call for a judge to review!
But wait, no judges!? I wanted blood, "Someone stat, hand me my digital mono-black deck, I'm out for blood!"
I digress, but I was getting my tail handed to me. I recently saw a deck with 250 cards and for this round, I chuckled. Side note, 60/60 is a standard deck size.
Most of my decks now average around 65 to 70. Adding just that added extraness.
So, try it out, the next time you want to rebrew your blue discard deck, toss in a couple of extra Unsummon's or Merfolk Secret Keeper, and see what you think.
Please though keep in mind, the more cards you have in your deck means less chance of getting the cards you need. 60/60 keeps the percentages down for drawing that one mana you need on turn 4. Yet, 250 cards drastically and statistically lower's your chance of getting that mana card on turn 4.
We can get into the algorithm of how MTG: Arena draws and shuffles your deck later.
Let me know your deck counts, and how the testing goes, will you?