3 minute walk to Arts et Métiers metro stop. 4 minute walk to a grocery store, Carrefour City. We 50/50 walked or took the metro to see things. Le marais is an easy 10 minute walk.
We walked from Paris Noord and wouldn’t recommend that. It was a long 25 minutes across a lot of crosswalks. Much easier to take the metro in.
We also bought the Paris Visite pass for 3 days for ~€25. I don’t think it was cheaper than paying for individual rides but it meant that we never had to stop and pay for tickets again, which was worth it for us.