Hi @Ced2ric,
As R1D2 mentioned, the Omada software doesn't impact the Wifi performance at all. How many AP's do you have? Which models? How are they wired?
You can also run Omada on a PC or if you only have one or two AP's you can configure them using the web interface in each AP.
You can also just run the Omada software temporarly on a PC to configure things and then shut it down.
Some general recommendations for troubleshooting new installs:
1) Start with one AP, connected via Ethernet to your router.
2) use a tool like inSSIDER to see what channels your neighbors are using
3) manually set 2.4 and 5.8GHz channels and start with the power set to medium
4) Use separate SSID's for each radio, don't use band steering
5) Disable Airtime fairness and Fast Roaming
6) Make sure the firmware is up to date on the AP
If possible, test Wireless link performance usng a tool like iPerf. If not, use internet speed tests (if your broadband is fast enough). Else, file transfers between a hardwired PC and a wireless client.
Start close to the AP (~5-10 feet away) run tests, then move farther away. Repeat for the 5.8 and 2.4 radios. Generally, for 5.8GHz 80MHz w/2x2 STA you should expect to see ~400-500 Mbit/sec DL and UL from this distance.
-Jonathan