One thing to note, if you are doing mesh with 4 IAP, that the mesh is over 5Ghz. If you are broadcasting the SSID on 2.4Ghz and 5Ghz and doing mesh over 5Ghz, you can hit situations where the backhaul and client access on 5Ghz creates some performane issues (the mesh trying to serve clients AND mesh can result in the mesh links not getting as much bandwidth as they need. A test could be to make all your SSIDs 2.4Ghz only which would preserve the 5Ghz mesh links for backhaul only, and see if performance improved. Overall, regardless, it will be faster, as testing has proven this over and over. But worth a shot to try if you're willing.