Help with multi-device selection for home Wi-Fi network

[Majdan]

I'd like to ask advice about how to design my WiFi network at home and suggestion waht devices to buy:
- It's a 3 story building with total 220sqm~2400sqft.
- Currently I use 4 mesh devices indoors (D-Link covr 1100), all connected with wired ethernet. It's two on the middle story plus one on the bottom and one on top story. Plus there are two two more same mesh devices that are outdoors and are connected to the rest wirelessly using mesh.
- The main issue is with dropping the connection on my iPhone. I did some research and it seems it's a known iPhones issue with some brands routers using 5GHz network. My D-links does not allow to name 2.4Ghz and 5GHz networks differently thus main reason for my project is to have this feature so I can tell iPhone to use only 2.4GHz in case it still have issues with 5Ghz.
- Another issue I am suspeciting is that my devices are too close to each other but due to existing wiring I probably won't change the placement of the devices. Also, removing some of them would create spots with too weak signal.
Thus I would like to turn off 2.4Ghz network on two devices and maybe turn off 5Ghz on one device.
- Probably I'd go with WiFi 6 or 6e as 7 might be too expensive and I don't even have a single reciever with WiFi 7 yet.
- I enclose NetSpot scan from few key places in my house:

https://imgur.com/a/ZKAmMb0

Questions:
1) What devices do you recommend? I do not like D-Link but I've used Asus and it seemed good. I've heard also about Ubiquiti. But there are two many options and I would appreciate some advice.
I would prefer not to spend more than 600usd for all new devices.
2) Do I need mesh system for my setup? Or maybe it will be fine with: 1 regular router, 3 access points and 2 repeaters?
3) Any other tips or workarounds? The biggest issue is iPhone problem with 5Ghz network.

 

[Tech9]

I would like to turn off 2.4Ghz network on two devices and maybe turn off 5Ghz on one device.

Consumer mesh sets won't allow you to do that. You need something like UniFi or Omada networks for this level of control. They offer individual per AP settings for SSID, VLAN, Tx Power, individual radio on/off, wireless mesh option. The budget is too low though for 4x AP system with the needed gateway, controller and PoE switch. You can mix and match consumer router with other routers in AP Mode or SMB APs, but you'll lose network segmentation options since not all the devices will have VLAN support.