A lot depends on camera load. Someone like
@SouthernYankee understands that chasing megapixels and 60 FPS is not needed on surveillance cameras. Too many newbies come here and buy 8 cameras that are 4k and want to run them at 60FPS and their network comes to a halt because they ran them through the router and the router isn't capable of pushing that much through it. And then add wifi cams to the mix and it is a recipe for disaster.
I believe it was
@SouthernYankee that did a test a while back on wifi cams and 4 wifi cams brought the router to its knees.
Having an NVR and you have the occasional video you want to pull off so you have it before the NVR writes over it is fine. However, most NVRs also have the ability to plug an external storage device to it and that would provide the fastest download of a video file.
So to review your footage on your phone, your NVR is going to have an IP address assigned to it. Then you just download whatever app the manufacturer of the NVR provides and you download it and plug that IP address in and you are off to the races.
However, keep in mind that probably also then gives you remote access and thus also the potential to be hacked, so if you truly do not care about viewing outside of your local wifi, you will want to lock down the NVR in the router settings from being able to talk to the internet. If you want access remotely, then I suggest you look at the
wiki for VPN solution.