Google MK5 Golf GTI tie rod and choose the Lemforder brand, which is the factory stuff. They don't usually come with outer joints, so aren't handed. If they do come with outer joints, pick the left or right side accordingly.
If it was me, I would replace both tie rods and both outer joints in one hit. May as well save on repeat labour and it will feel good and tight again
Yes as above, the rears do wear down because of the camber, and because they don't steer to even the wear out. It's a fair chunk of camber for a road car but -1.5 is the limit for acceptable tyre life. So long as it's just camber wear and not saw toothing (bad toe angles), it's fine. Although as a final caveat, saw toothing is what's considered 'normal' for MK5 GTIs and non driven wheels in general, so if providing it's not excessive, don't worry about it. Just change the tyres if the noise is getting on your nerves because it sounds like a bad wheel bearing!