Can the same sever accept both Explicit and Implicit FTPS?

As the documentation for implicit_ssl says:

To support explicit SSL and/or plain text too, a separate vsftpd listener process should be run.

For that see:
How do you setup multiple instances of vsftpd to run on different listen ports?

Though note that the implicit TLS/SSL is a legacy hack introduced decades ago to ease transitioning to encrypted FTP, at the times, when FTP clients did not have a built-in support for TLS/SSL. It shall not be used today. So the requirements of one of your client to use it, seems strange. I know of no FTP client that would support only implicit TLS and not explicit TLS.