Working Out Best Setup

[MultiBear]

Second; I am running this on one PC but I'll be using two different Battle.Net accounts - I own both though, so I'm hedging a guess this won't be breaking any ToS?

As Ughmahedhurtz stated, it's indeed no problem whatsoever as far as the TOS is concerned. However, you may want to consider requesting Blizzard to merge them for convenience though - something that should be no issue whatsoever if the contact details for both accounts are identical, so they can see they're yours.

Multiple WoW accounts on the same Battle.net account share things like mounts, achievements, pets and any 'Battle.net Account Bound' items (such as heirlooms, certain reputation tokens, etc.) can all be mailed between characters on those WoW accounts, which can be rather convenient. It also means your Battle.net / RealID whispers show up on all clients at the same time, which I personally quite like.