I bought the base model 13 inch M3, it works perfectly fine for your use case i assume. But if you can afford it and plan on to keep it for a long time (5+ years) then upgrade the specs. I always upgrade my Macbook every 2-3 years so 8gb is plenty for me at the moment.
Perhaps. But external storage also provides a different location for the storage of data that is not on the computer. Which will fail at some point, generally the most inconvenient time.
Not an either-or. The point being that if you have, e.g., large photo and video libraries that you want convenient, fast access to, you should get more storage in your main laptop for the outset. Don't buy small storage and fall for the argument that external storage is cheap. That's the path to having to carrying around an external drive and cable just to get your basics done.
But opting for more internal storage doesn’t mean foregoing getting an external hard drive for regular backups! That's to cover exactly what you bring up — the potential corruption or failure of the internal SSD or simply user error deleting a key file. Which is where wireless Time Machine backing up comes in, too.
I'm particularly those who pose the choice between more RAM or more storage as get more RAM because you can also add storage later. Nope! False choice or not equivalent. Get as much RAM and storage as you anticipate needing — from the get go. Don't shortchange yourself on the SSD front.