Both can be true, actually. As an aside, Russia truly lost in Ukraine in the first six weeks; most of their goals failed. Even if they were to take all of Ukraine, it would be so Pyrrhic as to not be a "win".
But, for the two statements: First: Russia cannot win in Ukraine. "Winning" is defined by history. There are lots of ways to end the war that will have Putin apologists claiming 100% victory, the best victory, everyone walks up to him and talks about his great victory, he's so powerful! So Russia is unlikely to take large amounts of Ukraine now; they have already taken the easy parts and are stuck on the medium parts. But if you change the "win" condition, he can easily win just by claiming victory (and having enough gullible fanatic to parrot his lines).
Second: Russia (well, Putin) will not want to stop at Ukraine once he declares victory and finds a few more Georgian votes. That seems likely, but he may have to stop, since Russia's military and economy is in terrible shape (as always happens after a long war). Putin is old, his allies in Russia are unhappy with the war, and his ability to wage war is far less than it was before he invaded.