@Terechia
The walk from Santiago to Finisterre is something apart from the main Camino. No-one (well nearly no-one) walks from Finisterre to Santiago but many people once they have arrived in Santiago choose to walk on to the coast. It has all the same things as the other caminos, albergues, yellow arrows marking the way and varied scenery, you can even collect stamps for a compostella, though this is not the same one as awarded in Santiago. The walk begins by heading down the stairs from the Cathedral Square and from there the path is well marked.
I think this has an advantage over some of the alternatives in that it's a complete route, it's not as crazy busy as the paths going towards Santiago and it may be easier to engage with your fellow pilgrims as "camino families" (the groups pilgrims often form) may be breaking up/changing/be more open to new people.
Once finished there are regular buses back to Santiago.
Whatever you choose.....Buen Camino,
Rob.