IMO, if you aren't using at least a 360mm radiator there's not a lot of point water cooling.
The point of water cooling is that you can transfer the heat from the heat producing component out to a large surface area by physically moving the hot liquid. 2x 360mm radiators give you a ton of cooling capacity. 1x 240mm? You can do almost as well for much less money with a really nice air cooler.
I'd also offer that it allows you to dump all the heat outside the case and avoid warming other components (assuming you put the radiator on an exhaust fan). This is a benefit with any size of radiator.
I literally just installed an NHD-15 and it dropped my idle temps 10 degrees vs my old AIO. Load temps are about 5-10 degrees cooler, too.
IMO, if you aren't using at least a 360mm radiator there's not a lot of point water cooling.
The point of water cooling is that you can transfer the heat from the heat producing component out to a large surface area by physically moving the hot liquid. 2x 360mm radiators give you a ton of cooling capacity. 1x 240mm? You can do almost as well for much less money with a really nice air cooler.
I'd also offer that it allows you to dump all the heat outside the case and avoid warming other components (assuming you put the radiator on an exhaust fan). This is a benefit with any size of radiator.
Even cheaper models are incredibly capable.