I believe what's wrong with your board is that WAVGAT is putting LGT8F328P microcontrollers on their boards which have been re-labeled as ATmega328P. I don't know who did the re-labeling, but there's absolutely no doubt WAVGAT knows their chips are no ATmega328P because they link from their official product listings to a specialized hardware package that is for the LGT8F328P. Even though they know this, WAVGAT clearly advertises these boards in the product as using ATmega328P and nowhere on the product listings do they mention that they are LGT8F328P so this is definitely a very unethical company.
Although not made by Atmel/Microchip, the LGT8F328P was designed to work very similarly to the ATmega328P that is used on the popular Arduino Uno, Nano, and Pro Mini boards. However, there does seem to be some differences that are causing the baud rate mismatch you encountered. You might try using this hardware package, which is essentially the one provided by WAVGAT, but with some serious bugs fixed:
There's another hardware package for the LGT8F328P that has been reported to be better than the one at the link above, even though it's not designed specifically for the WAVGAT boards:
I don't have any boards with LGT8F328P yet so I haven't tried either one out.