Interestingly enough, even back in the day Karn was extremely powerful as its Vanguard card was considered one of the strongest in the casual format, not too far off from players opinions of it as a planeswalker today
That means that if you play Frodo, Determined Hero when Swiftfoot Boots is in play - which grants hexproof and haste - you can attack straight away and it cant be targeted, and the attack will trigger the effect again, allowing you to put another equipment card on the Ring-bearer
In its prime, Glimpse of Nature was a rather consistent turn 3-4 win deck in Modern that used a lot of cheap elves, Green Suns Zenith and Regal Force to win games in the blink of an eye
For blue, it comes from the ability to draw cards, and colorless cards and land have the tendency to be especially dominant because they can theoretically fit into any deck (and the opportunity cost of playing lands is significantly lower than that of other card types)
Lets revisit Veyran, Voice of Duality
Because her draw ability triggers at the end of your turn, you are technically still in your own turn phase when you receive those new resources