Infloor radiant rarely uses water the same temperature as a typical radiator, regarless of the form factor. Radiators are usually designed for 160-180 degree water temperatures. An in-floor system might only use 100. Most boilers won't work well only heating to 100, so they use a mixing valve to get the really hot water down to temperature (it mixes in the cooler return water with the hot, then that is fed to the system). I doubt you'd need a mixing valve using radiators. If you use a smart modulating boiler, you can program it to generate lower temperature water when the conditions call for it. This can allow the radiator to be actually getting heat all the time, just not really hot, then off, then hot again...constant, just right temperature hot water would be more comfortable.