Best foldable car seat for travel

Hello! I am looking for favorite eu spec foldable car seat. I normally would not be looking for a foldable seat, but I need something we can tuck down into the bottom of the stroller while we're out and about and also easy to get in and out of a taxi quickly. We have a 16.8 kg 88cm 2.5 year old. We're american, but live in Germany. Sometimes we fly places and need the seat, and sometimes we drive our personal car, but need the travel seat for a taxi because it's just easier than trying to navigate ourselves. Thanks in advance!

I've looked at the:

cosatto on the go

Kindercraft fix2go

Maxi Cosi nomad plus