I forgot to say, the same is possible using Ivs and motion detection inside cam, when recording to a NFS storage (NAS).
Then you can decide if you would get push for Ivs or motion detection. I can't compare the motion detection to the QNap ones, but the data motion detection is not bad compared to my old non Dahua Cam's wich are nothing against it.
I also think, a NVR is normally more powerful. Par example the new 4.x Gen is able to use smart h256+ codec and build his own Ivs system. On every other ones I tested in the past, using of the bandwidth saver smart codec will also shut off Ivs.
And I like the smart codec, you need less hard disk space and also less upload so without activity you will get a stream for 1080p h256+ 4Mbit vbr6 with only 12kBit.
This saves many Harddisk space.