Yes, despite their anonymity and secretive nature, Anonymous is very reliable when it comes to information. They don't make things up. They hack into computer systems and mine information. Then they release that information when they see fit. These people are truth vigilantes. They unearth secrets that are based on fact, and expose them to the world. They don't do this to be vindictive or petty. Their motivation is to expose frauds to stop them from further hurting people.
I would be likely to believe evidence uncovered by the Anonymous group. They are generally a group of people who work to uncover and expose things that are being hidden by bigger powers, usually the government. I would assume that if they brough forth any damning evidence against Trump, the intelligence agencies will check it out and let us know if it is credible or not.
Any hacker can sometimes find 'real' information. My understanding is that Anonymous is a loosely organized hacktivist network, and if the hackers are good enough, they can often find really incriminating stuff. It's pretty fishy that the GOP has had a historic hardline stance on Russia, and that Trump who has financial interests there can't stop praising Putin.
If you look at where the "group" first started you would see why they can't be trusted. Being "anonymous" is part of the reason why you shouldn't trust them unless there's concrete proof to back it up as anyone with an agenda could push anything they want as "news" from the group.
They aren't hackers. Most of the group consists of people who have no idea of how to even program which as been proven countless times. One such case was the use of LOIC to take down websites as many had no idea that DDoS would land them in jail or that it could easily be traced from ISP records.
I almost think that Trump probably planted this guy to scatter the issue further and detract attention from himself. This guy is so ludicrous that he has to be a plant by somebody. I hope our intelligence agencies are not responsible because that would just be sad. I hope he is real though and Trump is impeached.