First of all, Gigabyte's UEFI bios seems to run mouse input at 10 or 15 frames a second. For it to feel laggy is completely normal and I've come across that in every Gigabyte UEFI board across both 1155 and 1150 sockets.
As for DVD drive booting, you need to check a handful of BIOS options:
1) USB support needs to be set to "legacy" for some external drives to be visible at boot.
2) Secure boot needs to be of (set to "other OS" rather than "Windows8") even if you're installing Windows8. You can change this to Windows8 after install if needed
3) Make sure the USB drive appears in BBS or drive order settings of the boot menu
4) Disable Ultra Fast boot. I think you can get away with Fast boot, but Ultra Fast skips the necessary <whatevers> for USB booting most of the time.
When you boot, mash F12 during POST and you should get Gigabyte's boot menu that lets you choose which device to boot off. This somewhat negates the need to setup drives in point 3 above.
Oh - I see you have an MSI Z87 now. I don't have any first hand experience with UEFI boards by MSI. I stuck to Asus/Gigabyte/Asrock these last few years. Certainly ASRock UEFI BIOSes are quite laggy with a mouse as well.
The above principles still apply, they may just be called something different in MSI's BIOS.
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