Multiple apps (microservices) and one proxy (nginx) docker-compose configuration/architecture
This is going to be an opinionated answer as both options are clearly possible.

I would go with the first option you described for the following reason:

It seems that at the moment you don't have a lot of microservices (otherwise you wouldn't be using docker-compose and would likely be doing k8s or at least docker swarm). Now, if your application grows a lot - you would likely outgrow compose in any case, so it would be wasteful if you optimize for compose at this stage anticipating future complexity.

So my take would be to go with option 1 for now which is much easier to implement. And when you need extra flexibility, likely you'd have other reasons to switch from docker-compose to something else.