You are wrong. Just did a search and came back with lots of sites saying you should add it in the time command

It appears that in Windows XP, 2003, and Vista, the Windows Time Service (w32time) will by default always try to form a "symmetric active" association with configured NTP servers. This can be problematic with some time servers, violates the published RFC-1305specification, and is not necessary. I could find no explanation on Microsoft's site for this behavior; I suspect it has something to do with interoperability with older Windows 2000 domain controllers that had very broken NTP.

However, there is a simple workaround. You can simply add ",0x8" to the end of any configured time server, and Windows will only use a client-mode association. For example, the command:w32tm /configure /manualpeerlist:",0x8,0x8,0x8" /syncfromflags:MANUAL /update
will configure your Windows machine to form client-mode associations with three differentNTP Pool servers.

Which NTP-server to use? Or several?

The is a round-robin of random selected NTP servers. As they say "This is usually good enough for end-users". But you might want to add several NTP-servers yourself for redundancy?

w32tm /config /manualpeerlist:"",0x8 /syncfromflags:MANUALJust keep adding them with a space in between them.