Hi @OldGeezer,

Welcome to the community!

Regarding your questions:

1. You're pretty much on the mark. The TL-WA855RE is a single-band (2.4GHz only) Range Extender that does not support OneMesh. In your application, it would be the most obvious bottleneck.

2. Again, your intuition is sound. 45 feet indoors leaves ample room for obstructions (walls, furniture, appliances, etc.) to significantly impact the connection between the Archer AX21 Router and RE220 Extender - especially for the 5GHz band, which is more susceptible to obstructions.

3. We recommend connecting all repeaters directly to the router for optimal performance. While it's possible to chain one repeater to another, we advise limiting this to two repeaters in a row to maintain adequate Wi-Fi bandwidth and quality. Depending on the model of the repeater, the concept of chaining may be significantly less ideal (e.g., in the case of your TL-WA855RE)

4. Powerline adapters can conveniently expand/extend Ethernet connectivity if both adapters are plugged directly into wall outlets tied to the same breaker panel. It may be an option to consider if you do not want to explore more modern and convenient whole home Wi-Fi solutions like Mesh (e.g., our Deco Mesh Product Line)

Hope that helps clear a few things up for you.

That said, for your case, my initial recommendations would be:

1. Relocate the RE220 closer to the router (depending on your home's layout and existing obstructions) while maintaining enough distance to optimally extend Wi-Fi range.

2. Consider replacing the TL-WA855RE with a more modern, dual-band Wi-Fi Range Extender that supports OneMesh or EasyMesh. You can reference our OneMesh Compatibility Page here, and our EasyMesh Compatibility Page here.

3. This one is more food for thought than a direct recommendation, but as referenced earlier, our Deco Mesh Products provide a more streamlined whole-home Wi-Fi solution for numerous connected devices since that's their primary design purpose and may be worth a look. One of our Wi-Fi 6 Deco Systems might suit your needs well, since Wi-Fi 7 may be a tad overkill for your existing Internet speed. However, if Mesh isn't something you're really looking for at the moment, then no worries—I just wanted to mention it in case it's a viable solution for your long-term networking goals.

Feel free to follow up with any questions you might still have, and I or other members of our community will be happy to chime in.