Regarding regions, sometimes in the Steam thread I've seen people using the
steamdb database. Basically you check the "Packages" of the game and see what regions are mentioned.
I have no idea what to make out of it since every region is mentioned but if you want to check for yourself
this is the page for Saints 4.
On a side note, I can't confirm anything for SR4 key but in the last week I've bought
GTA4 and
LA Noire from Nuuvem and they both activated without VPN on steam. In the past I've only once had and unusable key and it was
Inversion bought from Amazon.com.
Just because a seller is outside your region doesn't mean that you'll have to resort to a VPN but if you don't want to risk it I'll advise to wait a few days until SR4 comes out.
EDIT
Yes, Appid 29296 is Saints Row IV (BR). From what I've gathered the one on Nuuvem should be
Appid 28361 Saints Row IV Pre-purchase (ROW).
Nuuvem says the keys will be sent on the 23rd, as soon I receive mine I'll make an update here.