which decks require the biggest brain to pilot effectively?

i come from a hearthstone background, and i always loved and admired miracle and mill rogue for their extremely nuanced gameplay where the optimal play is extremely difficult to find and execute (unlike playing bodies on curve like most decks xd). tho, i never built one because i was intimidated by their skill requirement and didn't want to commit my real money into this risk xd (dumb $$$$$$$$$$$$$$ model)

gwent, being so f2p friendly, has inspired me to try such things that i love so much!!

so i wonder, what faction / archetype has the most thoughtful, detailled, nuanced, and, interesting gameplay, in your opinion? i love a deck that has many many options available at any given time, as it keeps things interesting

bonus question, at high ranks, which faction or archetypes are least common? i like to play the cool and interesting underdogs in games and try to make them work!