For the purposes of my comment I’m using the dictionary’s definition of ‘imperialism’, which is to say no, I’ve not read those author’s works.
As for your questions:
NATO is definitely involved, but Russia is not fighting them. I would liken them more to a boxing coach, their influence on Ukraine is massive and undeniable, but they’re only providing support, Ukraine is the one actually dealing (and receiving) the punches (Also the coach gave the boxer steroids but in this context its okay(weird reaching metaphor))
I’m not here to defend NATO, I’m not like a NATO-fan. I can criticize NATO and Russia in the same breath.
I simply do not believe Russia’s stated aims, much like the stated aims of the conflicts the US instigates it fails to stand up to scrutiny. What does ‘denazifcation’ of Ukraine even look like? Russia goal was regime change, hence why their first thrust was to Kyiv in hopes of immediately ending the war.
If Russia had immediately ended the war, it would have been a great success and put Russia in a good position. But they didn’t and now even if Russia succeeds and upends the Ukrainian government, it would seem like a pyrrhic victory given the circumstances.