Here's my take on it:
Anything other than
(DC-Copper runics)
Powerful Re-Forging
Grand Artifice
Inspired Artifice
(Bronze/Gold)
Powerful Re-Forging
Grand Artifice
Inspired Artifice
Exalted Artifice
Sublime Artifice
Is a waste. The brittle and weak items will break super fast and you cannot repair them nor POF them after reforging.
The more items you choose, the lower the power will be so you have to compensate with better runics. I've never thought about burning agapite or higher. Rather roll the dice and craft with them.
Never have tried with kits, but I'd say the same applies except lower Spined only go to inspired, Horned go to sublime artifice, and burn barbed kits like normal.
The idea is this: You want to maximize a property (or two in the latter case) so they are above normal imbuing levels. Then POF them, Imbue the properties you want on them after that. This is easier than it sounds because you can't decide during reforing how many properties you want. If you try using the a better runic for the first teir, you'll start getting random extra properties that you may not want- taking away your choice during imbuing. If you try for the latter case with a weaker runic, you end up with two weak stats as oppose to one that is overpowered. Even when doing it right- you run the risk of splitting the power into two stats. I.e.
(Copper)
Powerful Re-Forging
Grand Artifice
Inspired Artifice
--Vampiric Embrace
May give you a some certain 'power' but it might be split between HML and HLL. It's a dice roll, but after X attempts, eventually you'll get a single HML that is overcharged above the normal 70% HML.
Or in the case of bronze runics, you can get two properties above the cap or a mix of 3 or 4. So it does attempts to get the exact one you wanted.
In my opinion, this is used to create imbuing templates for items. Reforge to over charge 1 or 2 stats, imbue the rest with what you want.
In the end, I believe you can even attempt to enhance it to further boost it.
Don't forget to POF the item before imbuing. (but after reforging)