The majority of AIO coolers are manufactured using ASETEK technology. A Danish company who own several patents that OEMs use including Corsair, NZXT and EVGA.
It is a rather subjective topic and many cooler pundits have their opinions.
I have built several systems with AIO cooling and used Corsair and NZXT which offer good warranty for their products.
For my own use I currently have the Corsair H115i which is ASETEK 6th gen pump technology and keeps my Overclocked processor well under control.
Before you decide which is most suitable for your situation you should read some of the reviews out there and decide on the size that will fit your Case and the target Overclock you desire.
how about custom water cooling? what brand is reliable? im using the comp for mining when im not using the pc. i'll be using a lian li lancool ii mesh case. im using a aio 3090 evga hybrid cooler and the temp is not low enough when mining thats why im thinking of going custom water cooling on my next build.
An open loop is something you have to create yourself from scratch. Out of the box comes a separate radiator, pump, waterblock(s), reservoir, fittings, tubing and coolant which you have to custom assemble after you have decided on what you want.
Really for the extreme enthusiast , Lots of research if you want to get it right first time up from pump to liquid and fittings.
If you feel your up to it then yes they look great if done right but beware of leaks.
EKWB KITS offer quality preconfigured kits so all you need do is assemble as do Corsair Hydro X series.