If you're going to get infant carrier, go with stroller that can fit with the infant carrier, else might as well go for car seat that can support infant, since can be use for longer period. My first child lasted around 8 months in infant carrier, then had to use car seat due to size. Just need to make sure there is space for rear facing.

And before getting aftermarket isofix, incase you're buying seat with fixed isofix base, take note on how wide your door can open and how much room you have to navigate.

Bought nado o3 with fixed isofix base, quite an experience just to install on my car with limited door opening and tight rear space. No issue on wife myvi though due to 90° door opening and big rear space.

Sorry but not a good person to recommend since my infant carrier is not compatible with stroller.

But some infant carrier have adapter to fit different brand stroller, like maxi cosi carrier. Expensive but if you're in luck, can get it cheap on clearance sales like mamours warehouse sale on their display set. Bought mine for 60% less at mamours, and they will clean it up like new for free.