@Ohnopotato 

Here is a side by side comparison of the BE23 deco vs the XE75 pro

https://www.tp-link.com/us/compare/?typeId=5757&productIds=91685%2C59146

To keep the 6 GHz band you will need to keep the XE75 as the main. Doing this "may" cause you to lose out on the faster WiFi speeds on the BE23 units. 

If you're going losing the 6 GHz band then you can set your BE23 as your main unit. 

There are two ways to switch the current main deco to another deco i have posted both options below.

Configuring multiple models of deco units to operate concurrently.

If you have multiple models of Deco units, it is recommended to designate the new model as the primary Deco and the older models as secondary units.

There are two methods to achieve this. Regardless of the option you choose, please ensure that your network is configured according to either the first or second examples in this image: https://static.tp-link.com/upload/faq/image-20240329074344-12_20240329144345n.png.

**Option #1 (Not recommended)**: For guidance, please refer to the following link: https://www.tp-link.com/us/support/faq/2400/.

**Option #2**:

1. Reset all of your Deco units by pressing the reset button on each one.

2. Using the Deco app, set up your newest Deco as the main unit. Since you have factory reset each unit, you will be able to use the same network SSID and password as before.

3. Once the newer model is operational, return to the app and add the remaining Decos to your network.

  @Ohnopotato 

To answer that I will need the hardware version of your XE75 you can find it at the bottom on the unit 

  @Ohnopotato 

Just an FYI you can run the deocs in AP mode but there are a lot of features that work in router mode that do not work in AP mode

You can find the list of what works/doesn't work here https://www.tp-link.com/us/support/faq/2399/

  @jzchen 

Based on my understanding, and noting that I have not tested this in AP mode, when switching from Wi-Fi Router to Access Point mode within the app, it appears that those options are no longer accessible.

I believe that the options you may lose when running in AP mode would then be controlled by the modem/router provided by your ISP or the one you purchased yourself.

To the best of my knowledge, it is not possible to keep the BE23 in Wi-Fi Router mode while configuring the other Deco units in Access Point mode. The Deco app allows for setting up multiple networks, so you could designate the BE23 as one network and configure the other units as a second network in AP mode; however, I do not believe these networks would communicate effectively. Additionally, this setup could potentially lead to significant interference.