Hey, thanks for the reply. The second link doesn't work either as of this reply, it takes me to an error page with a "request timed out" kind of message. I suppose it isn't an issue though as it is just a generic CH341 driver. I've continued to investigate and one hypothesis I have is that this mystery nano is using a LGT8F328p chip, different from the ATmega328p chip that the official nano (and most clones) use.
The LGT chip actually runs twice as fast at 32MHz, but if the fuse bits are set incorrectly so it runs 8x slower... the result is a chip which appears to run 4x as slow as a regular nano, the same symptoms as your original post! I've yet to properly test this out and find the right drivers/libraries to install specifically for an LGT8F328p chip. There's more information about it here