Since both routers are routers - yes, I mean the same.
My opinion: Ignore the whole magic that might be possible, go with extender mode on your Flint 1 and you are good to go.
I don't fully agree with this 
Sure clients decide themselves which AP they prefer with 802.11r.
but if you compare this with 2 routers with the same ssid without it, then some devices see multiple ssids.
It doesn't look clean to me, like you see within mesh systems or just roaming in general.
With roaming you can cloak this visibility in the wireless list.
Plus some devices want to get stuck on one AP without 802.11r, but when you roam with this device in your house this is not handy, but what i found out with experimentation many devices which support 802.11r allow changing simultaneously better than without it, still it depends how well the device implements it, it's still their choice you can't control.
And compared to mesh, 802.11r is very old, so almost all devices support it. 