There's a tinycore tool - the tc-install extension - available in the CorePlus iso that will make a 32-bit or 64-bit legacy bios installation to hd or usb stick.
The legacy bios boot order is usually determined in the bios setup by choosing which device (hd, cd/dvd, usb stick, pxe) the bios should try to boot from first.
On my last laptop, uefi boot set the sata bus to full speed, whereas the legacy bios boot set it to a slower speed - since (I suppose) oem's now concentrate on uefi boot, you might be better to stay with that.