As
@stonjean633 already posted, better to spilt reasons:
1. Let the fastest devices use the fastest band.
To optimize throughput, put slow devices of 2.4 and faster on 5Ghz and gaming on Wifi6. This is because your router tries to apply fair use. What is fair use? Imagine your wifi being a train with say (when you have 4 devices) with wagons number A, B. C, D, E.. Then the Wifi networks gives wagons to every device in repeated sets of A-B-C-D wagons,. Problem is the slow devices occasionally mis a wagon, so your wagon allocations looks like A - used (fast device), B (used), C empty (slow device), D used next set of wagons A used, B used, C half used, D empty, etc.
So the fast devices end up in traffic jam caused by the slow devices (they could have used the empty wagons), because your router tries to find a middle ground.
2. Dump old protocols on 5 GHz and 6Ghz networks
This only applies when your device has more than one CPU to monitor and manage network traffic. When the CPU has less protocols to manage, it has a smaller reference set and assigns traffic a tiny bit faster because it does not has to look for slow old protocols
3. Last and best reason to spilt
2.4 usually broadcast stronger signal than 5 Ghz, therefore your fast gaming device get assigned to slow 2.4 Ghz network (because the signal is stronger). Then slow devices join in with old protocols (nearly all IOT devices use cheap old protocols because they have to send little data) and they have to be connected to your 2.4 network. So you end up with a lame half used router
Tip: set signal strenght on 5 Ghz to strong
