Are AIOs safe?
What are some of the best AIO brands/companies ?
Safe for what?
Usage? Like Leaking? Or protecting your CPU from meltdown?
AIO's have no general best brands.
They are all made by the same OEM, which is Astek, because Astek has a patent on the pump head technology and has taken many companies to court in regards to it, even the inventors of such concept which is swiftech, only because Gabe didn't want to be that guy and patent something which he thought would only be used in extreme scenarios.
But generally they are all the same, unless you got a company which makes its own like eK for example.
As for would i use it? Possibly only in niche conditions, otherwise i will go with the full custom setup, as distroplates can achieve the same thing at double the cost with double if not triple the performance.
So if im not counting ever last cent, then id go custom.
If budget is focused, id skip water all entirely and just stay on Air, unless your trying to cram the best cooling possible in speciallized ITX cases, which have been designed for an AIO.