ubuntu20.04.5,Two graphics cards display,After booting up, the screen only has the mouse。

My hardware configuration is:
CPU:i9-7980XE
MOTHERMOARD:ASUS WS X299 WAGE
GPU:2* ZOTAC RTX 3090

Problem Description:

My first question is:I can already edit the /etc/X11/xorg.conf,Implementing a single graphics card output when I start the machine。
But I can’t realize it. When I switch from the HDMI of the first graphics card to the HDMI output of the second graphics card, by modifying the file, I can only realize that only one graphics card can output at the same system startup. I want to automatic switching.I would like to know how to go about looking for an example of editing the xorg.conf file

My second question is:
When I connect two cards with HDMI to 2 monitors of the same model at the same time,I pass sudo nvidia-setting,Got the following interface。

When I check the settings as follows


After booting up, the screen only has the mouse。

This is my xorg.conf auto generated by nvidia-setting.
xorg.conf (2.6 KB)
nvidia-bug-report.log.gz (563.3 KB)

I’m really looking forward to getting some pointers

Please delete xorg.conf and set kernel parameter
nvidia-drm.modeset=1

I didn’t make it clear just now. I know that after deleting the /etc/X11/xorg.conf file through ssh, you can restart and enter the normal system interface, but the problem is that I don’t know how to use the HDMI output of multiple graphics cards. The correct configuration method

By setting the kernel parameter, see
https://forums.developer.nvidia.com/t/ubuntu-20-04-not-able-to-run-6-7-monitor-setup-with-one-x-screen/200904/2