@justdave
Things I can tell you:
Kasa:
1) Most times failure to configure them seems to come back to user error and or W--Fi issues. Eg: Many IOT things don't like sharing an SSID w/5g and 2.4ghz networks, etc..
2) Most switch failures are in the solid state switching relay. There have been cloud/app problems too, but that's not a pervasive thing.
3) Warranty is a joke. You'll spend enormous amounts of time jumping through support hoops, then document proof of ownership, and finally getting to ship the failed unit back at your expense.
4) The products are quite inexpensive.
5) As you can see, we're not going to get any insight into what products have more reliable architecture.
6) TP-Link owns Tapo, so I fear that's jumping from one dumpster fire into another.
7) From what I can see of the architecture and product spec's the hardware selection is based on "cost is the most important factor".
8) Limited Matter support, don't expect it to be stable any time soon either.
9) Pretty wide product selection.
10 Plug failure rate is horrible.
11) Switch failure rate is so far OK, but I'm more than a bit concerned.
12) TP-Link technical support states the plugs are not to be used on a power strips, and are only capable of 2.5amps unless using a purely resistive load. Meaning if you use a capacittive on inductive load you're limited to 300 watts. Things like PC power supplies, most TV's and monitors, stereo's, fans, you name it aren't able to be used in any meaningful way.
13) TP-Link support forum reports some dimmers only support 150 watts of "equivalent" LED's. Meaning you can't run three 60 watts LED bulbs and be in spec. They're probably wrong, but it just adds to the "these are cheap toys" feeling.
Feit products:
1) Very reliable from a failure perspective, but a vary narrow product set.
2) Their dimming technology is very bulb finicky and prone to flicker
3) Support attempts to be responsive but is undermanned.
4) I've never seen a software or firmware update.
5) Wifi range is the lowest of the products I've used, especially for the plugs.
6) Relatively inexpensive. I've bought quite few from Costco.
7) You can use their dimmer switch in a 4 or even 5 way situation.
8) No Matter support, don't expect it.
9) Not easy to wire, sort of poorly designed relative to it's peers.
Leviton
1) Relatively expensive, think 3x Kasa cost, but stable in all regards. 0% failures to date!
2) Super stable on dimming, wifi connection, and installation.
3) Very wide product selection, including battery "remote" switches that can go anywhere and control other Levitons.
4) Matter support is rolling out, to what degree it can be retrofitted I've no idea.
5) Fantastic technical support. Really really good.
6) No observed range issues.
7) Haven't used their plugs (yet)
Emporia:
1) In the switching realm they only have energy monitoring plugs
2) They appear to be stable (too soon to know)
3) Support is pretty good.
4) Based on use of the Vue products, I expect firmware support to be limited.
5) Matter support = No
6) In the "relatively inexpensive" ballpark.
7) Power rating: 10 amp continuous, any type. 1 hour max per day at 15amps.
So here's where it stands for me:
* As Kasa product fail they will not be replaced. The disrespectful warranty process ends their viability as a mfg. to me, their product reliability is unaccepable, and ratings shenanigans are really shameful.
* Topo will be part of the same culture, so nope.
* Feit: For 4 way plus dimmers they are the solid choice (and you only need 1), as is Leviton with their companion remotes. Just know you'll be replacing batteries annually for the latter, and the former has lots of limitations. Solid choice for on/off too. Just poor as a dimmer.
* I'm moving to Emporia for future plugs, but reliability of them is not clear.
* The hassle of pulling and replacing failing wall switches has implied cost. I will replace with Leviton.
As to Alexa, I'd call their tech support. It's not great, but sometimes you get lucky. My experience has been most of the times issues with integration lay at their end. BTW, Alexa devices can do funny things with more than one in the house. If you do, I suggest you unhook them all, plug only one in, and rediscover devices with just the one running.