To start off, I've never flown one of these nor have I seen one flown -- it's a fairly new airframe.
From a quick glance, it looks like a fair compromise between a sport flyer and a glider. Fairly short wingspan at 1.3m and the high cube wingloading at 5.8g/dm^3 (4g/dm^3 is the upper end of a glider -- your Radian ranks in at about 3.4g/dm^3) will hurt the glide performance, but the motor seems trimmed for a cruise flight.
It looks like a fun flyer, but more a floaty sport plane/trainer than a glider. The AS3X, surprisingly, helps tremendously with the UMX Radian, so I'd lay good odds the Adagio will be better off for it. I wouldn't expect it to thermal soar well, but it should fly fairly slow and friendly.
If you're truly wanting to move up to a 4/5 channel glider but still stick with a foam construction, I'd suggest the RXR version of the Flyzone Calypso -- For foam, it's fairly good performance, the Flaps are an easy mod, great payload capacity, and she can hold a moderate thermal well. Horizon did an amazing job with the Radian, then such a poor job with the Radian pro -- a fine plane in it's own right, but nowhere near the performance of it's baby sister plane it's supposed to be the "pro upgrade" for. Flyzone learned from Horizon's mistakes and found a nice happy medium with their Calypso -- I'm thrilled with mine.
BTW, Welcome to the forum!