On Acer Aspire R11 (R3-131T-C56L) .. FB renders unusable, X won't start, boot only in "safe" mode

I tried installing LEAP 42.1 on an Acer Aspire R11 (R3-131T-C56L). After some struggling with the UEFI BIOS I was able to boot from an USB net-install image.
I had to select Kernel “Safe Settings” to be able to boot the installer system. APIC failed, but the noapic option alone was not enough to start up correctly it seems…
Anyway, using those kernel safe settings I could smoothly install Leap on the laptop, overwrite the complete disk (hence wipe Windows).
But when the system the rebooted, I was presented with a graphical GRUB where text was displayed line per line, character per character. GRUB is very slow in responding to keystrokes as it is constantly busy refreshing the time-out line character by character.
When actually booting into leap, I see grub loading the kernel and initrd image… then suddenly all characters on the screen become unreadable rounded white blocks and after a while I see the screen refreshing a few times (which I asume is Xorg trying to start up) and then get a console login (I assume as it is still unreadable white blocks, but it resembles the console login screen :-))

Does anybody has any idea where to start to get Leap working ? How can I make the font readable for starters… Then I can probably start looking into why X is not starting…

It seems to be solved:
For the above installation I had used Legacy BIOS as I had problems booting from the NET-install USB stick in EFI mode.
Now I retried the installation with the Full DVD on USB, with UEFI and secure boot all enabled again… And now GRUB(-efi) as well as FB graphics and Xorg seem to work as it should be…
I have to note that I also upgraded the BIOS of the laptop from 1.04 to 1.09 (Fixed factory INT15 9610 0150 no display issue.)
Now I also didn’t have to disable APIC to be able to boot. Only ACPI had to be disabled otherwise the screen turned black after udev initialization.
Don’t really understand how UEFI could make such a difference… ?
Or are there things wrong with the NET install ?