The 2018 Tiguan has been using the same 6R0-915-105-B battery since it was new. Now we were getting codes about voltage on many modules so it was time to replace it.
I went with the same battery I put in my 2016 GTI earlier this year, a Duralast Platinum H6-AGM 760 CCA. Its been working well for me so figured it was worth getting again. Due to me changing from a Led Acid to AGM type battery as well as the Tiguan having a BEM module followed these instruction using my VCDS to make the appropriate changes https://www.golfmk7.com/forums/index.php?threads/how-to-retro-fit-a-bigger-capacity-battery-to-a-mk7-golf.320084/
I topped it all off in the end with turning the wheel lock to lock (all the way left then all the way right) to clear common codes related to a battery disconnect.