I've been myself in such position years ago and my focus was on growing my team, making sure help is provided where needed, people talk to each other, we regularly synced on strategig frontend matters. I knew exactly what skillset we have and what we need whenever we had an opportunity to hire. In my particular case, I was not only line manager, but I led the whole frontend technology in the company. So both. That's how I ideally imagine this role (without going to much into topic of delegation, giving responsibility to the team, etc).