Seat Alhambra (equivalent to VW Sharan): with 2 adults & 2 children's bikes -> as described, bikes are folded back on the floor space to make room for the boot door. I see no reason why this should not work with the slightly smaller Touran - it is designed exactly for this purpose and works perfectly! Highly recommended!

It also works with 2x ebikes weighing 20kg each and a 6x road bike.

Yes, if you fold the bike carrier forward, it works. You can also fold the bike carrier forward with bikes on it. But it probably depends on how heavy the bikes are.