The highest output of the 2.0 TDi engine was 170 PS but the same size of engine (bore and stroke) is now putting out up to 190 PS as standard. What physical differences are there, if any, for these higher outputs? Bigger turbo, injectors, stronger bottom end?

Since the 170 PS engine will remap to 200-210 without reliability worries, the structure of the engine is unlikely to have been upgraded. The injectors and engine management software as well as the ducting/exhaust, DPF and turbo are likely to be where they did the tweaking. I'm not sure if this information is available anywhere though. The only way to find out may be to go to Elsawin and compare part numbers.