From talking with Nat Bradford, I know Taiwanica can easily survive the border of zone 8a/7b in the US South, and if it does suffer damage it will easily recover, but I'm not sure how it will do in the same zone classification further north in a cooler climate.
You should at least plant it in an optimal spot, not completely out in the open.
I have difficulty imagining it will like zone 7 Germany.
Could probably grow in zone 8a part of Germany, but not 7.
I doubt it's hardier than Yuzu, probably similar.
As for the Citradia, I'd imagine it would have no problem in 7b but not sure about 7a. Might suffer some damage most years but could then recover, due to its sour orange parentage which is pretty vigorous growing.
Disclaimer: I do not grow these two varieties, but have lots of experience growing many others, all different kinds, rare Japanese varieties and strange hybrids, so I think I do have some intuition on this.