Following along, my tank is similar, and I'm at a similar stage, but my coral goals are different than yours (mostly LPS maybe low demand SPS, not huge on sticks) but maybe my thoughts would be helpful....?
I just ordered two xr15's for my new 120. It seems the general consensus on the forum is that this may be a bit underpowered/stretching the reach of the lights to fill the tank.
There are a lot of costs when setting up a new tank and I didn't feel the need to start off with $1700 in lights while the tank cycles/stabilizes. I won't be starting with expensive or high demand corals within the first several months or year, this setup should provide me enough light to start growing what I like and several paths to upgrade in the future if (when) needed.
My plan when needed is to add the Aquatic life T5 Hybrid, I also have a center brace so having 3 LED/puck lights doesn't seem to work, and going to 4 XR15's is a big step up in cost. With the center brace I think the fill from the T5's will be important and the T5's + 2 XR 15's should grow everything I want. I Imagine even a fair amount of SPS especially closer to the pucks.
If/when more power is needed I'm guessing the Hybrid +4 XR 15's should be able to grow about anything on a 48" tank, and so if I decide I want to grow a bunch of sticks I have a clear path to do so. I've read about people using three XR 30's on a 4' tank for high SPS growth but again with a center brace this seems difficult to place and I would be pushed towards the hybrid. Again though take this with a big grain of salt right now as this is purely hypothetical and I'm not an SPS guy.
The basis of this all is that the XR30's are basically the same price and output as two XR 15's, Generally you get more flexibility in terms of when to spend money and light placement starting with XR 15's. For this reason I felt like there was very little downside to starting with 2 xr 15's no matter what the next steps would be since I could simply buy more if needed and not lose anything vs forking over the money and starting with the XR 30's off the bat. If my thought process is wrong I'm sure somebody will chime in below, and look forward to others thoughts.
(this is all assuming you are set on using radions, as I'm sure others may recommend comparable AI or other lights which are also good options, just not my ultimate goal or vision for the tank)