If possible, I would suggest setting a common standard for all weapons within each category. Like similar pivot positions, rotations, etc for all swords. That would save you a lot of headache in the future, especially if the game is going to have lots of weapons.
But if that’s not an option at all, then try out each of the meshes in your character’s skeletal mesh preview and note down the required rotation for each of them. You can then add this data to the data table for each weapon and use it to set the correct rotation while spawning the weapon.
As for switching between meshes vs blueprints, Faithdrawn and NebulaGamesInc have already provided the solution. If all your weapons function similarly, then you just need to change the meshes.
But if they fall into different categories like a hitscan rifle, projectile based rocket launcher, melee sword, etc then it is better you create child blueprints for each of them. So that way you won’t have 100 blueprints for 100 weapons. You have one for each weapon type and while spawning the weapon, you set its mesh using the data table info.