Araknis WAPs? Is mesh best? If so, why do manufacturers continue to make non-mesh WAPs?

I have three Eero's and it's handling our needs well. That said, I use it for a two person house. This is not your situation.

The Araknis 700's are designed to be permanently housed, and more for professional usage rather than the Home market the Eero's aimed at, so they would make more sense. Do you have the 700's currently positioned, with the ports facing downwards? Have you checked to make sure each one is currently plugged into the PoE? Also, have you used a WiFi scanner to check for dead spots?

I'd say Mesh is best for home usage.

The main thing to remember with these technologies is that they each have a use case.

I've used this analogy before; imagine you're trying to tell your friend a story, but this friend happens to be on the other side of a field and can't hear you shouting. You need some method of getting the message over to them.

Lets say you're using two access points, one is your router, the other is in another part of your house and hard wired into your router. In this instance it's like having a second friend stood next to your first friend. You can call either one of them, they can put you on speaker phone and you can tell the story - either way your first friend gets to hear it directly from you.

If you're using a range extender/repeater - this is like having a second friend stood in between you two. You can shout to your friend in the middle, then will turn around and shout your message onto your first friend. Now depending on the distance you may end up having to add more friends into the field, while it sitll may work, there's more chance for the message to be changed by the time your friend firiend gets it. This adds a delay and the possibility of losing some of the message; thankfully your first friend will shout back what they've heard so you can confim they've got the right message...but that all adds a delay.

Mesh networking is more like all of your friends having a conference call, then you can walk around and just speak your message to anyone who's listening. Your first friend will still be able to hear it because you're walking in range of someone on the call. The downside here is that sometimes you'll be close enough to one for it to be crystal clear, other times you'll be between two friends so there's a bit of an echo as you're being picked up by more than one phone.

This is sort of what happens with mesh networking and is why it often disconnects like you've described. The phone has to make a choice between which signal it connects to, while the system itself is also trying to negotiate and grab your traffic. When we set these systems up in a professional setting we tend to map out overlapping signals where you're not likely to be moving. Effectively choosing where the dead zones will be.

Mesh networking is still hugely under development and is constantly improving, but each approach has its downside. The setup you're using is robust, like the first approach, but you're still contending with a device that's trying to cling onto its currently assigned AP. You'll find that you need to give the device a little jog, either by going out of range entirely or forcing a reconnect (turning off the wifi or disconnecting from the AP) for it to pick the best signal.

I use a PepLink Balance 210 Router and 6 PepLink AP One Mini AP’s that are all connected via Ethernet. The Balance 210 Router has an on-board AP management system but I can also use their subscription Cloud Service to manage all my PepLink devices. This system is designed for an office of 150 users however I use it in my home and it is very solid. Previously I had an ASUS System with ASUS AP’s and it often would not hand off my mobile devices. Managing my 4 ASUS AP’s was also a lot of work. My PepLink System is huge overkill and a bit more complicated than the average consumer grade system and of course it requires Ethernet to the AP’s but it is transparent in use.
I also run an outdoor AP as well that is connected via Ethernet. 
For a Mesh System, I am impressed with the AmpliFi HD Mesh System which I helped a neighbour install.