There may be several problems, there is not enough information to determine which one it is.
1. There may be dfs signal detection
2. Could be interference from another station
3. Maybe one user is occupying the entire internet channel.
and a few more.
Create a detailed description
Right now I can say the following you have a very low signal from clients for a distance of up to 600 m. If properly configured Litebeam M5 can work at a distance of 5 km or more. By adjusting exactly the direction to the antenna you should get the maximum signal Tx in the registration table. You have to get a signal stronger than -60 (now it ranges from -64 to -40) Then by adjusting the power on the client you have to set the Rx signal to about the same for all and again it has to be -60 or stronger. (right now it ranges from -75 to -58)
You have all devices of standard n, so select "n only" in the settings. This will slightly increase the overall performance of the network.
For the Omnitik 5AC, it is more correct to choose ac devices. Microtic SXTsq 5 ac, DISC Lite5 ac, LHG 5 ac or Ubiquiti LiteBeam 5AC LBE-5AC-23
PS On a device that receives -40 signal I would remove the side lobes of the dish, which would reduce the gain
If I select Band 5Ghz N only then what will be the impact on my client?
They will work smoothly or they have a data transfer limit AP to station when selecting 5Ghz N.
I want to travel 20Mbps of data to every client.
I bought Omnitik 5AC because I have a few clients in Omni 360 within max 600 meter
But until now I'm unable to analyze whether the Ominitik 5AC fully fills my needs or if I need to move to find another solution.
Before this, I was a Ubnt user. Now I'm going to fully Mikrotik product. (but sometimes these kinds of bulshit problems confused me).