I have tried both the Radeon Test Day and the standard X86_64 ISOs booting them from a USB drive I created using the Live USB tool on F10. It makes no difference if I use the Radeon chip (aka Discreete Graphics) or the Intel chip (aka Integrated Graphics). In each case, F11 Beta boots to a blank, white screen with no visible text.
The first thing that comes to mind is syslinux. F11 on live-usb requires a new version of syslinux than that in F10.
From your your regular F10 install do
#yum --enablrepo=rawhide install syslinux
and then create a live-usb again as usual. We have had a number of people(myself included) who got around to booting successfully by using Rawhides' syslinux.