Grip: It depends in part on what your non-ranger profession is. If you are in a profession that uses a lot of enchanting, the 20% enchating grip could be useful. For pretty much everyone else -- defense, defense, defense. You can get a +4 defense grip for 200 gp and a +5 (perfect) for 5K or less.
Strings: I use three bows most of the time. I have a max+15>50 longbow (from the dune burrower jaw collector in the desert) that I use for pulling. I stuck a shocking string on it so I'd remember which it was (the collector bows all say "Ascalon" as the only descriptor), but the string type doesn't matter that much for a pulling bow. I have two max+15>50 shortbows (troll trusk collector in the S. Shiverpeaks) that have, respectively, a zealous string and a 5:1 vamp string (available for 60-75K) on them. Both have +5 defense grips. Customize those bad boys and you're ready to go. Strings of any other type are not that great, except the specialized case of poisoner's strings if you're going to be doing poison damage to mobs or fire/ice/shocking/ebon strings if you are an elementalist who's using conjuring skills. Sundering strings = waste of money, hands down. They do minimal bonus damage, especially when compared to the +5 unconditional damage done by a vampire string or the almost unlimited supply of energy you get with late-game shot-spamming skills + a zealous string. Don't let anyone tell you otherwise.

Hope this helps.
Edit to add: The advice above assumes you're doing PvE with minimal HP damage from superior runes. If you're using superiors a lot, you might be better off with a fortitude grip (30 HP is the max). This advice comes from a very trusted source (most of it is from him) and from my personal experience (minimal as it is).