I had the SEAT version of the Tiguan Allspace the camera was quite good in terms of resolution and clarity. However, one of the annoying faults on mine was that after a few seconds of reversing the screen would blank itself for a few more seconds and then go back to normal.
It had a self cleaning function when you used the rear wiper which was quite clever. Not sure this is the same system as the Tiguan.
When I had an older Leon, several dealers indicated that you cannot retro fit a camera because the head unit is different and the utilise a different wiring loom. At the time I found it hard to believe but had no way of easily checking.
To me it made no sense having different head/display units and a different wiring loom. Even the £380 does seem and excuse my VAG to charge customers a significant amount for something that should be a standard feature these days especially in terms of safety