I'll do this in parts in a different order.
Why would you NOT enhance a reforged (armor) item? You can't enhance Jewelry, and the only reason to enhance a metal weapon is to change the damage types or add more luck.
BUT, Armor can be enhanced to improve resists - especially now that most metals and leathers add 4-5 more resists than they did prior (16-17 max instead of 12-13, depending on skill - Spined leather had an all-physical increase, while metals and other leathers got an additional 1% to each resist). This might require using a forged metal tool to have 100% chance to succeed (as the chance without it might be 0% to 5%), but those extra resists can completely shift a suit build.
Woods have other properties, that affect both weapons and armor. Heartwood can have one random property that people will sometimes make many reforged items and attempt enhancing to get at least one with the desired property. Bloodwood can add 2 HP Regen (and is the luck material for shields) to items that don't have HP regen yet. Frostwood can add Spell Channeling and DI, in addition to cold damage, as well as adding high resists to armor.
And, shields (of any materials) are the easiest things to enhance to improve resists.
6 suit parts, enhanced, can have 100+ more total resists than a suit without enhancement - 120+ if including a shield. That's potentially 6-8 or more property slots not used for resists during the item creation process. I typically take the materials I intend to enhance with already calculated, then figure out what resists the reforged parts have to add up to be.
For example, if I don't care about luck (say, if you're going to use a macro to switch to a luck suit for the kill), you can look at the following
6 Valorite parts: 70/70/70/70/70 - 30/0/24/24/24 = the suit needs to total 40/70/46/46/46 after reforging, but before enhancing. Therefore, you make multiple base items (exceptional metal armor parts that have 15 fixed and 20 random resists), and choose for the ones that have high fire resist. If you start with each item having 11 or better fire resist, you will be at 66 or higher fire. This would leave you 38 resists (on average) short of all 70s - UNLESS you reforged one item "of Fortification" to get a 70-110 total resist item (or loot one - they are REALLY common). With this combination you can have 5 reforged items that you don't have to improve resists on - especially if you end up using a shield (1 base resist, up to 17 additional resists from enhancement, and some shields can be looted or crafted that have one or more +resist properties)
6 Barbed parts for a med suit: 70/70/70/70/70 -18/12/18/18/30 = 52/58/52/52/40. the base parts of the suit are 2/4/3/3/3, so that's 12/24/18/18/18 + 120 random resists, or 40/34/34/34/12 - 120 random resists, or 34 resists you have to get from properties (or less with resists on shield).
Luck suits tend to be more complicated.
Reforging can produce overcapped powers - that's what drives it.
I don't like having so little control, either, but it's better than no control at all with conventional runic crafting. I do wish they'd make the total intensity for conventional crafting with runics to have a higher power pool.