[RPG] Do you need a magical bow or arrow for Arcane Shot

You don't get the buff, because the very first part of Oathbow reads:

When you make a ranged Attack roll

And with these spells, you don't make a ranged Attack roll. So nothing happens with the Oathbow.

Your Attack Reveals You

I am not sure whether a creature getting banished makes any noise. It's possible that the creature disappears without any sound, or that it vanishes in a flash of light screaming. Either way, that isn't what will give you away: it's the attack you needed to make to banish the creature.

Banishing Arrow states that:

The creature hit by the arrow must also succeed on a Charisma saving throw or be banished. (XGtE, p. 29)

Since you need to hit a creature to banish it, you needed to make an attack. However, the rules on unseen attackers and targets state that:

If you are hidden—both unseen and unheard—when you make an attack, you give away your location when the attack hits or misses. (PHB, p. 195)

Note that it doesn't say you give away your location only to the target of the attack. When you attack while Hidden, you lose your Hidden status. Naturally, you wouldn't become visible to someone miles away, but basically anyone who could have been alerted by an "ow" from your initial target has already been alerted by your attack. (You can't even get around this with the Skulker Feat, because your attack needs to have hit).