There have been lots of threads on the T5-R, T5 and R variants of the 850/70 - but briefly, the T5 is a high pressure turbocharged version of the standard vehicle with mild suspension upgrades and internal and external extras depending on spec. and year.
The original T5-R was a homologation special of the BTCC Volvo estate in limited numbers (500 in the UK) and only available in black and yellow, I believe.
Then the model was productionised to become the 850R and 70R, with a slightly stronger engine construction and a top spec. that includes leather/alcantara electric seats, ECC, TRACS, electric everything and either Volans or Titan wheels depending on year.
They are instantly recognisable by the lower stance due to harder suspension, the low front bib and the rear spoiler - the saloon model has a grey insert on its spoiler.
The US models are all auto, but as has been said, 250bhp manuals have come into Canada, though the power differential is pretty marginal provided the auto box is working properly.
I also understand that US models may have a higher ride due to the appalling state of US roads; though all pictures of US Rs I've seen look the right stance to me...