RTMP/UDP, which is "faster"?

[C0D3]

Hello Dears

First, thanks a lot to all those helpful posts here.

So i try to implement a screen capturing setup with Piwall. I definitely have no clue about Network architecture :).

I made a local RTMP Server with NGINX on a linux Mint computer.

The problem 1 is I have a latency about 2-3 seconds. 

My Setup:
1x Router FRITZ!Box5490

1x Allied Telesyn FS708 10Base Ethernet Switch with 100mbs

4x Raspberry Pi 4 Model B 

Everything connected with Cat 5 Ethernet cables

So the NGINX server is on a MAC computer with Linux mint. I communicate with parallel-ssh to the Pi's with it.
Id like to Stream from another Computer, a Windows and OBS.
So this actually works well, but like I said, with alot of latency.

Question 1:
Is there a difference in Speed or Latency with the "direct" UDP way of send Video, to this RTMP setup with nginx?

There is this a way to communicate over UDP with OBS with the Record function. So i tried actually to do this with the Same setup.

Problem 2:

With this Setup I cant send anything over the UPD address 239.0.1.23:1234.
It works well when im doing it from the Linux Mint Mac computer, but not with the Windows computer which is on the same local Network.
I tried to turn off Firewall, do a port forwarding on the Router.
Idk, something is wrong, the Windows cant address this UDP successful. 

Question2:

How is this happening? I can send over the RTMP server with this Windows Computer, but not over this UDP address.

So i hope someone can help me. And i hope you understand my Problem :)..