In the first case...he only went after sections of Georgia that had high concentrations of Russia sympathizers...and similarly, that was the case with Crimea...in fact, it's my understanding that Ukraine's Admiral in charge of its Navy 'defected' to Russia in the aftermath, so Putin probably had plenty of inside help with that operation...not a lot of risk there.
Not so sure that he'd try to take over all of Ukraine, since he's never taken on serious risk of big losses and defeat before...the only 'bite' I see him taking is Donbas and that would likely incur fierce and continuing opposition from Ukraine, proper...possible, but not the move of an insecure bully...guess we'll all have to wait and see.