are you running 4k 60hz or higher on the monitor?
your ideal case is to run display port to your monitor (or even display port to hdmi adapter) and HDMI to the TV, then you can duplicate the screen virtually in your graphics settings and save the headache of splitting signals.
HDMI 1.4 will not be a downgrade unless your monitor is very very new and has HDMI2.0 connectors. everything in the path needs to be HDMI2.0 for all the features to be available, it's likely your monitor is only HDMI1.4 or 1.3 so the TV and the monitor have the same connector. Your graphics card is futureproof for the next generations of HDMI 2.0 4k 60hz HDR TVs and monitors.