The bitrate is independent of the dimensions. It is expressed in Kilobits per Second or Megabits per second.

The relationship is exactly this:

File size (MegaBytes) = Bitrate (Mbps) x Time (Seconds) x .125

You can see that Resolution is not a factor.

At the same Bitrate, different resolutions will display different quality accordingly. That's where your own tests are the only determinant. Experiment. A lot.

x264 is the most compact encoder practical for your resolutions.

So I assume then I need to reduce 5000KB/s ? Yes/No?
If that is the case to maintain as much quality as possible should I use 1080 with Lower KB/s or reduced KB/s and 720 . Will lowering the KB/s lower their data consumption?
We use black & white boards for teaching so we need video as clear as possible.
 

I had a look at a random videos on YouTube just then AVC 1080P30. trump at a news conference Video1700kbit/s, something with a lot of movement was 2700kbit/s. Try 2500kbit/s perhaps at 1080p30 and see how that looks. I would keep the 1080p as it makes a big difference when reading the screen. Ideally you'd use voukoder for encoding as it can encode based on quality rather than bitrate, and for something like a classroom setting with a whiteboad it may set the bitrate quite low. For quality settings, try CQ 24 and keep going up if bitrates are too high for what you'd like. This is not an encode to be further compressed by an encoder this is the final encode that you'll be streaming or sending and the recipient will see. You are aiming for acceptable quality (eg youtube quality)

Or is there another way to "skin the cat" with lower data rate and as good of quality,

Yes. I have spent much of this year investigating that, and exploring deep-state compression techniques, while maintaing very good quality and preventing peak rates from causing hiccups and stutters at the viewing end.

If your lessons are all more or less "the same" in terms of motion and complexity, I'll be glad to give you some optimized starting points, using x264 HD, which is universally playable. Send me a couple of ProRes or XAVC-S or XDCAM-EX masters via Drive or Dropbox, and I'll send you some suggested render proofs and the optimal x264 params.

Or is there another way to "skin the cat" with lower data rate and as good of quality,

Yes. I have spent much of this year investigating that, and exploring deep-state compression techniques, while maintaing very good quality and preventing peak rates from causing hiccups and stutters at the viewing end.

If your lessons are all more or less "the same" in terms of motion and complexity, I'll be glad to give you some optimized starting points, using x264 HD,

Yes it's been my experience, x264 at low bitrates self destructs at same bitrates where NVENC still looks acceptable. You need to contain the peak bitrates.

This is how Instagram does it

• cabac=1 / ref=1 / deblock=1:0:0 / analyse=0x1:0x111 / me=hex / subme=2 / psy=0 / mixed_ref=0 / me_range=16 / chroma_me=1 / trellis=0 / 8x8dct=0 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=0 / threads=8 / lookahead_threads=2 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=1 / keyint=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / rc_lookahead=10 / rc=crf / mbtree=1 / crf=24.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / vbv_maxrate=2912 / vbv_bufsize=5825 / crf_max=0.0 / nal_hrd=none / filler=0 / ip_ratio=1.40 / aq=2:1.00

And this is how TIkTok does it. Both are aiming for the best compromise between lowest bitrate and highest quality for that low bitrate. IG chooses crf24

• cabac=1 / ref=5 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=8 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=30 / lookahead_threads=5 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=3 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / rc_lookahead=50 / rc=crf / mbtree=1 / crf=29.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / vbv_maxrate=4000 / vbv_bufsize=8000 / crf_max=0.0 / nal_hrd=none / filler=0 / ip_ratio=1.40 / aq=1:1.00

Thank All of you for the Help. Greatly Appreciated!