The smoke under the hood is probably going to be burn off from a leaking valve cover, the exhaust smoke could be from a burnt, stuck, or floating valve. Worst case could be oil blow by in the cyl from worn rings. If there are no codes, that still doesnt mean that youre in the clear, that just means its not picking up when you scan, i.e. not causing a misfire etc. How many miles does the motor have, and how hard do you push it? I would do a cyl comp test and I would get some new valve cover gaskets, while youre in the valve covers check the spring tensions for each spring and put new valve seals in there since youve got all that apart anyway. But I dont think this is going to be a miracle can fix, this could be several different things, start small and go big. Or , take it to a shop that knows what its doing and have them take a look. Good luck, hope this can be of help.
" Buy the ticket , take the ride......" Hunter S Thompson