I have a suggestion that you may try to implement.
There is a project for multiboot ISOs (before Ventoy ever was). It includes a script (or instructions if you prefer) to create a hybrid multiboot USB drive and a set of ready-made grub config files to auto discover ISO files and create grub menu to boot them.
There is no Garuda config, but I have created and used one for my needs. Maybe you can confirm it works, so we can start suggesting it.
Original project and Webpage
Forked project (original stopped adding/fixing issues)
Save this in the relevant USB (or project) path, at (check relevant) /boot/grub/mbusb.d/garuda.d/generic.cfg
for isofile in $isopath/garuda-*.iso; do
if [ -e "$isofile" ]; then
regexp --set=isoname "$isopath/(.*)" "$isofile"
submenu "$isoname ->" "$isofile" {
iso_path="$2"
loopback loop "$iso_path"
probe --label --set=cd_label (loop)
menuentry "Start Garuda Linux" {
bootoptions="img_dev=$imgdevpath img_loop=$iso_path earlymodules=loop misobasedir=garuda misolabel=$cd_label nouveau.modeset=1 i915.modeset=1 radeon.modeset=1 logo.nologo overlay=free quiet showopts"
linux (loop)/boot/vmlinuz-* $bootoptions
initrd (loop)/boot/initramfs-*.img
}
menuentry "Start Garuda Linux amdgpu not-radeon" {
bootoptions="img_dev=$imgdevpath img_loop=$iso_path earlymodules=loop misobasedir=garuda misolabel=$cd_label nouveau.modeset=1 i915.modeset=1 radeon.modeset=0 amdgpu.modeset=1 logo.nologo overlay=free quiet showopts"
linux (loop)/boot/vmlinuz-* $bootoptions
initrd (loop)/boot/initramfs-*.img
}
menuentry "Start (nvidia proprietary non-free drivers)" {
bootoptions="img_dev=$imgdevpath img_loop=$iso_path earlymodules=loop misobasedir=garuda misolabel=$cd_label nouveau.modeset=0 i915.modeset=1 radeon.modeset=1 nonfree=yes logo.nologo overlay=nonfree quiet showopts"
linux (loop)/boot/vmlinuz-* $bootoptions
initrd (loop)/boot/initramfs-*.img
}
menuentry "Start Garuda no nVidia" {
bootoptions="img_dev=$imgdevpath img_loop=$iso_path earlymodules=loop misobasedir=garuda misolabel=$cd_label nouveau.modeset=0 i915.modeset=1 radeon.modeset=1 logo.nologo overlay=free quiet showopts"
linux (loop)/boot/vmlinuz-* $bootoptions
initrd (loop)/boot/initramfs-*.img
}
}
fi
done
This config for Garuda provides different choices, depending on video hardware, which may or not do much difference. I was experimenting, but it would be nice if you test them with your hardware and provide feedback.