Qos how to properly approach the organization of traffic flow?

Question

Mikrotik

Good afternoon.
The question is 5 Mikrotiks. Connected via GRE without encryption, etc. on each 2 channels to different providers, (always one works, the distance is set) OSPF routing. There was a question about the need to allocate a guaranteed bandwidth for Sip, Rtp traffic.
I smoked the manuals on the organization of Trees, etc. basically all the manuals written from version 2.9 to 5.0 in the 6th version of the queue were reworked. Now: What is the best way to do it 1) Organize through simple queues as they say in the manuals (allocate a band between two IPs with a set limit, for example, let's say 5 mb), for example, from a voice gateway to Mikrotik and from Mikrotik to PBX, but will it work correctly. And in general, I don’t fully understand how it works, one moment, the band in a simple queue starts to be allocated at the moment the transmission, traffic starts, or it is already guaranteed to be given away and no one can use it (rather no than yes).
2) Limit a specific list of addresses for speed, thereby freeing up bandwidth (although there will still be plugs in mine), and not limiting the desired addresses.
3) Dig deeper, mark incoming outgoing traffic, highlight Layer 7 RTP and make it a higher priority on other types of traffic.
3) Maybe there are better ideas, I will take into account any more sane guide (you need to understand how it works) The language is not important, we will disassemble it.
Still there are no softphones, all voice gateways sit in a separate vlan and separate subnets. Everything converges on Mikrotik.

Answer 1

If somewhere there is a channel of 10 Mbps to the Internet, and there is a tunnel to another office, where there are files and a voice, then qos will not save. Users will kill 10 Mbps instantly, and qos only works on outgoing traffic...