Hi Interfaces,
first question, are yours lightspots recessed in the ceiling?
If yes, slightly move them down until they are completely out and you should see a big difference in term of noise
Then switch to Path Tracing, set the GI Clamp at 10 or below with a bit of Choerent ratio (between .35 and .5)... the render should be cleaner, brighter and faster then DL Diffuse
With v3, you can also increase the parallel samples to speed up the calculation even more
Last question, is the Gamma of the ies file set to 1?
ciao beppe