OpenSSL TLSv1.3 record padding OpenSSL supports TLSv1.3 record padding:
https://www.openssl.org/docs/man1.1.1/man3/SSL_CONF_cmd.html
but I'm not sure if it works like I think it does. If I would choose a factor of 2 it would make the record (=packet/payload length???) twice the original size. Is that correct? If so, wouldn't random padding be better? Otherwise you could just divide the packet by 2,3,4 ... to get to the real value?
If I would choose a factor of 2 it would make the record (=packet/payload length???) twice the original size. Is that correct?

No; if you set a factor of 2, then the encrypted record size would always be even (that is, if it would have been odd, a padding byte would be added).
In general, a factor of $x$ would increase the size of the encrypted record from 0 to $x-1$ bytes.