Hey Evalery,
one has the impression, that no matter what machine one has, it´s never fast enough...
I bought an iMac Pro 8 core some months ago... pretty fast thing.
And now some guys here in the forums who use the Threadripper with 32 cores claim that my machine is "not a render engine by any means". :)))
In my opinion, this endless spiral of more and more cores and power should be compensated by more intelligent algorithms in the render engines.
As you said, Corona is a great renderer... my absolute favorite - especially due to its great light calculation and resulting aesthetics.
Nevertheless, a few improvements could save us from this crazy, never-ending race for GHZ. So we could focus on creativity.
P.S. on my machine, denoising takes literally just something like 20 seconds, even on large images.
But as mentioned, edges with high contrast, like on metal parts take endless render time until they have clean antialiasing.
Should be improved... in my oppinion.