@Popcorns:
mate, your q is multifaceted IMHO....
firstly, the best method of oaking,
per se, is in with largest oaksoak you can acquire and with the longest time accordingly.....and lessens with size, pretty much accordingly...(i.e barrel best, then stave, then stick , then chip, then splinter, then sawdust, then faux-oak essence)....the simple difference with regards to your spirit is wash recipe/quantity of ferment/time.
Secondly, an on topic

if using most whisky essences...these will (attempt to) provide an oaking-like result, regardless of additional influence (and Aidan has stated such may become a prob)...so take care, else you'll likely end up with alcoholic wood drink.
Alternatively, there are better ways to make Scotch mate (I know, I've tried many) and, it depends on the 'level' where you are happy/able to produce. As stated above, all I can say is a decent AG wash and a decent stilling (I use a potstill, twice) will ALWAYS provide potential for a more satisfactory outcome.
Oh....and regardless of any tosh above in my post, please consider this:
DON'T MIX essence base with AG, DONT mix Scotch with Bourbon....or, ay least keep decent quantities separate for control/taste tests later
