OK. Thank you.

Perhaps you can point me in the right direction here. If not, no big deal I'll continue to research but here's my situation.

I used to own a home that I had hardwired. I had the equipment listed above, plus two of these and one of these. I primarily followed this three-part YouTube video and also this video from crosstalk.

I have now moved to a new home that I rent. I will be hardwiring but only to a room or two. Nothing extensive. For the AP's probably.

Anyway, I still have all of the network(s) credentials and (I believe) IP's from my devices.

I think I would like to restore all of the equipment to factory settings and then go through the process of setting it all up again as a learning tool.

However, I would prefer to restore and update all the equipment before I switch anything related to my current gateway (like putting it into bridge mode). Is this advisable and/or possible?

There's another way you can go that's even better, but if you're just in an apartment it's not really necessary. If you move into a house later on, it's absolutely the best way to do things.

To understand this, you need to understand that what you think of as a "wireless router" is actually three devices combined into one: router, switch, and access point. The router moves data traffic back and forth between different networks, allows multiple devices to share the single IP address that your ISP gives you, blocks unwanted internet traffic from reaching your network, and assigns IP addresses to devices on your network. The switch is what gives you the four Ethernet ports on the back, it moves data around within a network by keeping track of what's connected to each port and only sending data it receives to the correct port. It's actually a six-port switch, the other two ports are internally connected to the router and access point. The access point is the part that does Wi-Fi, it's the "wireless" part of a "wireless router".

So, what you should do is pretty simple now that you know this. Instead of getting a "wireless router", you can get your router, switch, and access point separately. This has three big advantages. Each device can do its job better as it doesn't need to do two others as well, you can put them in different places that are ideal for the function of each device, and if you need to replace one of them, you can keep the others.

For example, this is a router. You'd connect its WAN port to the modem or ONT, and the LAN port to a switch, such as this. You'd connect any Ethernet devices to the switch as well. Lastly, you'd get an access point and connect it to a PoE port on the switch, which will allow the switch to power the AP through the Ethernet cable. This can be expanded as far as you need it. Need Ethernet ports elsewhere? Connect another switch to the first one. Need Wi-Fi there as well? Connect another AP to the second switch. You get the idea. The only downside to all this is that everything needs to be connected with Ethernet cables, so it's not really feasible for an apartment.

I'm only on 60/60 since I'm not the account holder, but my setup is more than capable of handling gigabit. It's way more than you'd need for a basic UniFi setup. All you need for a basic setup is either a UDM (which is an all-in-one device) or a USG, switch (doesn't need PoE, AP includes an injector), AP, and controller (which can be installed on any PC, it doesn't need a standalone device).

This is my network rack. The equipment is, from top to bottom:
Keystone patch panel
US-24
Shelf with Raspberry Pi 3B+ (for Pi-hole), US-8-150W, USG
Cloud Key Gen2+ in its rackmount adapter
Rackmount surge protector
Oh, and this is the rack itself.

The ONT is off to the left and connects to port 1 of the patch panel and port 1 of the main switch. Ports 1 and 24 of the switch are in a separate "WAN Passthrough" VLAN which isolates them from LAN traffic. This wasn't necessary, it just makes the wiring neater. Port 24 on the switch connects to the USG's WAN2/LAN2 (configured as WAN since WAN1 died), and LAN1 connects to the LAN via port 22 on the switch. Port 2 on both the patch panel and main switch goes to the 2nd floor, I was only able to run a single Ethernet cable between floors, so this goes to another PoE switch that powers the 2nd floor AP. The rest of the lines on the main switch go to Ethernet jacks in various rooms. Ports 3 and 4 on the patch panel are connected to the PoE switch, and power the basement and first floor APs. The PoE switch also powers the Raspberry Pi and Cloud Key. Its four remaining ports will be for security cameras. The Cloud Key Gen2+ serves as a NVR for UniFi Protect (in addition to running the UniFi Controller), so everything's all ready for them.

The two switches are connected by their SFP ports in order to not take up any of the normal ports for this purpose. I used two pairs of these transceivers and two of these cables, which actually was cheaper than using RJ45 SFP modules. The SFP ports are set up as a link aggregation group on both switches, so they essentially become a single 2 gigabit link, avoiding any bottlenecks.

The basement AP is a Lite and the 1st and 2nd floor APs are Pros. The Pro has since been supplanted by the NanoHD, which is my main recommendation for heavy-use areas. The Lite is still perfect for light-use areas.