Welcome Fish17. Re your questions, your list looks very similar to ours. If the info helps great. If not, someone else may offer something you can put to use.There's a a lot of information on the forum and in the wiki. so reading is your friend.
2.4 Ghtz is going to be stronger and reach farther. 5 GHtz for the devices that can make use it and almost all devices can use it depending on walls, density and construction in the home. The 3200 can automatically pick and choose the radio if you lose interest in tweaking, for optimal results.
Your questions didn't reference VPN, but if you are assigning static IPs, the following link can help you avoid problems that can crop up if IPs aren't within a certain address range;
Edit; please see;
https://github.com/RMerl/asuswrt-merlin/wiki/Policy-based-routing-(manual-method)
Step C, #3, and ** Important.
You can also assign one or more devices by assigning a static IP based on mac address; in the OpenVPN Client tab, set Redirect Internet Traffic to "Policy Rules". Then, enter the IP of the device you assigned, 0.0.0.0 for destination IP and VPN for iface. (per Xentrx).
As long as the static IP's assigned are in the correct range re the above wiki, more bandwidth will be available for your iPad, laptop and other wireless devices if you can connect your gaming console and Apple TV via Ethernet. Some streaming TV units no longer offer you the choice of using Ethernet. The closer your WiFi TV devices are to your router, the better and faster the streaming will be. I always save the radios for iPads, phones if possible. The three guest networks are useful for guests, devices or gadgets so I use them all.
2.4 GHz gives you a stable fast connection at longer distances. 5 GHz usually offers you higher speed and throughput, the closer the device is to the router. If your iPad or Apple TV (or Switch) uses concurrent 5 GHz AC, use the radios to get the higher speed and performance from the fastest devices. Depending on the number or type of devices on your network, how much RF noise from the neighborhood bleeds into your home, can be a factor where manually assigning higher bandwidth devices to a certain radio using a different SSID may help you distinguish which device or groups of devices use which radio. It's not included in your question but you may want to research it. Some don't find this method helpful and it's not for everyone. Using different SSIDs on some of the radios has proven useful to me.
Setting up your radios and static IPs can be fun with the 3200 (or is for me), and using SSID can help define combinations that offer you the best speed for some devices on select radios. Remember to save your settings or keep screen grabs in case you decide to start from scratch. You can try turning off all devices, then starting with the fastest (or slowest), work your way down (or up) through the radios with each device or group of devices. We have a Dot within 10 feet of the router and another in the next room on the same guest network. You can rename the Dot and may want to turn the microphone off when you don't want the Dot to listen in. Hope this helps; post if you need clarification.
