But if the recast metal on edges causes the lams to have electrical continuity with each other then your rotor losses will be higher. The lams are supposed to be insulated from each other.
We never welded, we always used the rotor bars as 'rivets' to hold it together.
No it doesn't change anything as the damage is very shallow. Some people us an light abrasive to remove many edge buts that might form from the cutting, but as long as you are not being overly aggressive they should be fairly smooth.