Smoke on startup is leaking valve guides. Lots leaks while it sits, and vaporizes (NOT burns) when you crank it off. Bet it smells like oil spilled on a hot exhaust, right?

Bad rings will show smoke on engine braking, as the vacuum pulls oil past the rings. It will smoke all the time, and smell like BURNT oil, but smoke a lot worse on decel.

I'd put a quart of ATF in the oil and get the seals to soften/swell, then change the oil. Run it with the atf about a week or so.

Not responsible for advice not taken...