Signal strength and range of newer wifi routers

Generally, with one exception, hand-off is controlled by the device. On devices where the roaming aggressiveness can be adjusted, usually laptops and PCs with Wi-Fi adapters, it's sometimes possible make hand-off low-impact, but it often is neither transparent nor non-disruptive. I don't often walk my house with my laptop streaming, so personally this is not an issue.

On the other hand, smartphones often do not have adjustable roaming aggressiveness settings, but these are precisely the devices with which we want transparent handoff. My old iPhone 5S was terrible at roaming at home and at work.

If you install a second WAP in your house, you should not expect transparent hand-offs. But, like I said, it's usually up to the device.

I did mention one exception, well maybe two. One is that there is a Wi-Fi standard called 802.11r that governs fast hand-off. I don't think any consumer Wi-Fi gear implement it. Two is that Ubiquiti Networks offers a proprietary feature called Zero Handoff where multiple Ubiquiti APs can work together to hand-off a device between them. I don't know which of their products offer this feature, but my guess is that they aren't cheap. The downside of this feature is that all the APs must use the same Wi-Fi channel (they make all the APs appear like one AP). That's not so good if you have a lot of Wi-Fi devices and need a lot of bandwidth. It's a trade-off between speed and reliability.

I would recommend you try one of the higher end Netgears with external antennas. If you are happy with your current router and only need an AP, then consider the EX7000. It's marketed as a wireless extender, but it in fact can also be used as a wired AP. It'll be cheaper than the R7000. But if you want to upgrade your router, then the R7000 is a great choice. I have one and it covers nearly my entire 2 story house.