The table shows the version each transmission speed was introduced in. HBR3 speed was introduced in version 1.3. No new modes were added in version 1.4.
G-Sync doesn't work through DP hubs.
That would be unlikely.
It says they're getting support for the VRR protocol from the HDMI 2.1 standard. That doesn't have anything to do with increasing the bandwidth. And it's unlikely the signaling rate of the HDMI controller in the GPU could be tripled with a firmware update.
That's what I said would happen
1440p 144 Hz requires about 14 Gbit/s, 120 Hz requires about 12 Gbit/s.
DP 1.4 supports maximum of 26 Gbit/s, which is enough for two 1440p at 120 Hz, but not 144 Hz.
1440p 144 Hz requires almost a full DP 1.2 connection. DP 1.4 is only 50% more bandwidth.
I think you should be able to get dual 1440p 120 Hz. But most DP hubs only support DP 1.2 bandwidth anyway.
Two 1440p 144 Hz monitors would exceed the maximum bandwidth of a single DP connection, so hubs won't work in this case. You would need a graphics card with 3 DP outputs.
4K 60 Hz HDR is outside the limit of HDMI unless you use chroma subsampling.
None of the passive adapters/cables will work since they will be limited to HDMI 1.4 speeds. The Club3D adapter should work though.
Go to NVIDIA control panel under the Change Resolution and make sure Output Color Format is set to YCbCr 4:2:2 or 4:2:0 if you really want to use HDR.
Sometimes on laptops with switchable graphics, the ports are limited to 120 Hz at 1080p. There is no fix unless the laptop BIOS has an option to use dedicated NVIDIA GPU only instead of switchable graphics.