Essentially no processors follow a standard. There are some that have become a de facto standard and had both backwards compatibility and clones produced like x86. But it is certainly not an open standard, and many lawsuits have been filed to limit the ability of other companies to produce compatible replacement chips.
RISC-V is an attempt to make an open instruction set that any manufacturer can make a compatible chip for, and any software developer can code for.
Bear in mind also that the extra weight and possibly aerodynamic compromises actually reduce range. In some cases, particularly at night, in poor weather, and at high speed, the panels would be a net negative.
They would only be useful if your car sat around in the sun for long periods without access to a charger.
HDMI and DP do not carry their signals in the same way. HDMI/DVI use a pixel clock and one wire pair per colour, whereas DP is packet-based.
"DisplayPort++" is the branding for a DP port that can pretend to be an HDMI or DVI port, so an adapter or cable can convert between the two just by rearranging the pins.
To go from pure DisplayPort to HDMI, or to go from an HDMI source to a DP monitor, you need an 'active' adapter, which decodes and re-encodes the signal. These are bigger and sometimes require external power.