The title is self-explanatory, so I won't elaborate too much, but my picks for the most reputable channels are Linus Tech Tips and Digital Foundry. Linus may be click-baity to a fault these days, but I am 100 percent convinced he knows what he's talking about, despite how often he drops his products. He's even been surprised a few times when some products that sound like they'll be garbage, kinda end up not being so. Digital Foundry also talks about graphics in games in a mostly objective manner, but when they give subjective opinions, I usually agree (I like modern motion blur in games. This isn't 2007 anymore.)
Least reputable however, aside from The Verge (remember their terrible PC Build video?) is... honestly, I'm not as big of a fan of Joker Productions as I used to be. He seems to rely heavily on sketchy sponsors these days, which have ended up leaving me out of over $100 with nothing to show the few times I gave them a shot. He is also very strong headed, and even contradictory on some of his opinions (framerate to be exact) and his "optimal settings" guides for some games don't appear to be quite optimal, with some settings for his Red Dead Redemption 2 video being lower quality than the XBOX One X version. I personally can't play RDR2 without long shadows on, but I know that's a subjective thing for me, and not a point of his own video.
What are your picks?