TGGeko:
If the Arduino is interfacing with a device that uses two stop bits, will there be a problem if the Arduino uses the default serial config? Would there be issues with reading from the device, or writing to it?
Certainly not reading from it. The extra stop bit would be seen as a slight delay before the next start bit.
Sending 8N1 to a device that requires 8N2 could easily cause framing errors and may cause almost every character to fail. If the receiving hardware actually CHECKS for a second stop bit it will usually find the next start bit instead. Since they are of opposite polarity it would signal a framing error.
If the devices receiving hardware is not checking but is depending on that extra delay to set up for the next character it may start looking for the next start bit too late. If the rising edge happens before the hardware is ready to sense it the next byte will also signal a framing error. The hardware will have to wait for the next rising edge to use as a start bit. This is probably in the middle of the character. Then it will count off the 8 bit times for data and look for the first stop bit.
You should send whatever format and bit rate the receiver requires.