I think the i-frame interval setting is inapplicable when H265+ is enabled, so the field gets disabled or hidden. In that case, don't worry about i-frame interval.
How many of what size hard drives do you have?
Do you need to record continuously (24/7), or is recording on motion detection acceptable?
If we assume 24/7 recording to one 32 TB hard drive then like I said in my earlier post each camera needs to average around 1852 Kbps or less being recorded. This needs to account for the main stream, the sub stream (if that is recorded, I really don't know if it is or is controllable on most NVRs), the audio stream(s) if any, and a little bit of file format overhead. So you should not actually assign 1852 as the main stream's video bit rate. I would probably go with about 1500 Kbps there in the Max Bitrate box, and decrease the frame rate until 1500 Kbps falls within the recommended range. Then I'd configure the sub stream to be perhaps 128 Kbps and probably the same frame rate as the main stream. And the audio stream, if there is one, should be kept fairly small. AAC codec. 64 Kbps is probably sufficient if that is an option. Then your total bit rates would be 1500 + 128 + 64 = 1792 Kbps per camera, which leaves a little room for other overhead that I mentioned.
You could do significantly better with two 32 TB hard drives because that would let you double the bit rates, and 3000 Kbps is going to be significantly better main stream video quality than 1500 Kbps.
Also remember if some cameras are less important you could assign lower bit rates to them and higher bit rates to others. Just as long as it all averages out to a rate that won't fill your storage in less than 120 days.
