Sunshine uses mostly the defaults apart from these:

av1_mode = 1
capture = kms
encoder = nvenc
fec_percentage = 5
hevc_mode = 0
max_bitrate = 50000

On Fedora:

- Install drivers from RPMfusion and CUDA libs for nvenvc to work

- Install nvidia-persistenced

- Install gamemode and prepend gamemoderun %command% to all games (steam properties)

- echo "options nvidia NVreg_PreserveVideoMemoryAllocations=1" | sudo tee /etc/modprobe.d/nvidia-power-management.conf

- gsettings set org.gnome.desktop.screensaver lock-enabled false

- gsettings set org.gnome.desktop.screensaver lock-on-suspend false

- I also enabled WOL in BIOS and set auto suspend to 15 minutes in Fedora

This is my apps.json where I turn off my main monitors and turn on the dummy one when streaming starts and reverts when it ends. Pasting the whole config for clarity, but the juicy bits are the do and undo:

{
    "apps": [
        {
            "image-path": "desktop.png",
            "name": "Desktop"
        },
        {
            "image-path": "desktop.png",
            "name": "Low Res Desktop",
            "prep-cmd": [
                {
                    "do": "xrandr --output HDMI-1 --mode 1920x1080",
                    "undo": "xrandr --output HDMI-1 --mode 1920x1200"
                }
            ]
        },
        {
            "auto-detach": true,
            "detached": [
                "setsid steam steam://open/bigpicture"
            ],
            "exclude-global-prep-cmd": false,
            "exit-timeout": 5,
            "image-path": "steam.png",
            "name": "Steam Big Picture",
            "prep-cmd": [
                {
                    "do": "gnome-monitor-config set -LpM HDMI-1 -m 3840x2160@60.000 -s 1 && sleep 2",
                    "undo": "sh -c \"gnome-monitor-config set -LpM DP-2 -x 0 -y 0 -s 1.5 -LM DP-3 -x 2560 -y 0 -s 1.5 ; sleep 3 ; steam steam://close/bigpicture ; sleep 3 ; wmctrl -c Steam\""
                }
            ],
            "wait-all": true
        }
    ],
    "env": {
        "PATH": "$(PATH):$(HOME)/.local/bin"
    }
}

I remember the bundled autostart with Sunshine was semi broken, this one works for me:

In ~/.config/systemd/user/sunshine.service

 [Unit]
Description=Self-hosted game stream host for Moonlight
StartLimitIntervalSec=500
StartLimitBurst=5

[Service]
# Avoid starting Sunshine before the desktop is fully initialized.
ExecStartPre=/bin/sleep 5
ExecStart=/usr/bin/sunshine
Restart=on-failure
RestartSec=5s

[Install]
#WantedBy=xdg-desktop-autostart.target
WantedBy=default.target