Ok, I would have to run some more tests, but I tried many baudrates and even 921600 did not give good results at the time.
Thanks for trying to work out my problem 
Going by https://www.raspberrypi.com/documentation/computers/configuration.html#configuring-uarts, you are using /dev/serial1, which maps to ttyAMA0 (UART1), which is the mini-UART PL011. The PL011 mini-UART is on /dev/serial0
This is what I get from the link you sent. Isn’t it the other way around then ? I mean, I would be using serial1, which is a symbolic link that points to /dev/ttyAMA0 (in my case, given the screenshot you reposted above). And according to that table, that’s the first PL011, UART0…
Correct. That was a typo in my post. I’ll fix it up.
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To answer this original question, it might be actually better to use serial over USB (CDC-ACM) since it has CRC and is probably more noise resistant than UART. It also has built-in flow control and should be baud rate independent.
Different UARTs on RaspberryPi are pretty interesting, had no idea this could cause issues.