If you have pps, then do use the prefer and iburst keywords with this
server(s) on your client machines.
If you have pps, there is no need for more than 3 or 4 total servers
in any machine's configuration.
FYI I run two pps servers, one is a Pi with a GNSS receiver and the
other is a Ubuntu machine with an oven controlled precision crystal
oscillator reference GNSS receiver.
The pps servers configurations includes 3 network servers which serve no
purpose other than to keep the selection algorithms sane. Do not have
the pps servers reference each other.
All the client machines use the two pps servers and two network servers,
which also server no purpose other than to keep the selection algorithms
sane. The pps servers have the prefer and iburst keywords.
Because of the way the selection algorithms work, you need at least 3
servers in any given client's configuration, so I have 4 just in case
one of the remote servers is dead on a restart.
I log all statistics and do graphing of all the machines on a web server
so I have a good idea what everything is doing.
If I reboot a client, it typically takes a minute or so to select one
of the pps machines, about a half hour to get to the 10's of millisecond
accuracy, and a couple of hours to get to the 10's of microsecond