I wonder what servers are set to receive normally.

I can go up to a 100, but if the server only takes 50 for instance, then there's no real point in that I guess. So what would be a good setting for that?

Per second?

The default value matches the tic rate, which is by default 20 per second... But demos look better with a higher cl_netfps. I use 30, but I know that some people go up to 100. I'm not sure it helps a lot for gameplay, maybe someone else knows.

if you mean the ping:
the 100 is the time a pack need to come (i dont know seconds or µseconds...) ...not 100 packs an a time

I'm talking about the "Input Packet(s)" in the Network settings.

Yep, that's the menu control for the cl_netfps cvar. And it's Input Packets/s, "/s" meaning "per second"