I booted the system using DFSee - how I discovered that CSM needs to be Enabled to boot from CD/DVD on this system
It sounds like you and a bunch of other people are about to run into all sorts of avoidable problems for lack of some basic info.
First... there is no such thing as a "UEFI CD/DVD" or a "[CSM] CD/DVD", there are only UEFI and CSM *bootloaders*. The menu gives you a choice of which one you want to use on the mounted optical disk. If the DFSee disk you burned doesn't include a UEFI bootloader (not your doing), then it won't boot in UEFI mode and you'll be forced to use the CSM bootloader that it does have. Had you tried booting an AOS5.1 DVD, its very likely you wouldn't have encountered this problem since it contains both.
Next... TTBOMK, DFSee has never been updated to fully support ArcaOS's GPT implementation. In its current state, DFSee can read and write the entire disk *except* for the partition tables which it can only _read_. Without additional code that talks to the GPT driver (GPT.FLT) and coordinates its activity with LVM, it can not be used as an OS/2 GPT partition editor. You can still use it's other features such as creating partition images or copying them to a new partition, but in the latter case that new partition will have to be created by MiniLVM.
Do I reinstall Windows11 or copy existing install from the 128Gb SSD using DFSee?
Good question
Do you have a Win11 DVD or is this a preinstalled system? If you have an install disk, then do a new install to the NVME drive, letting Win create the ESP (EFI System partition). After it is up and running, then install 5.1 (it isn't at all fussy, as Martin discovered).
Be aware that the issue of Secure Boot will come up during installation. My impression is that if you decline it, your system will be "disadvantaged" in some way (you'll have to check the MS docs to see if this is really the case). If you opt for it, you'll have to register AN's Secure Boot key with your system for the two to coexist. (Doing so manually is pretty easy on a desktop system and likely impossible on a laptop. There's a yet-to-be-released utility that will make it fairly easy on any type of system.)
OTOH, if you have to copy the partitions to the new drive, you're going to need a lot of in-depth knowledge of how Win navigates a GPT drive and how to use 'bcdedit' (or whatever may have replaced it). I'd suggest an exhaustive search on the topic of moving Win11 from one drive to another (it ain't easy!).
What creates the EFI System partition and the starting and finishing Fsp + GPT partitions
Typically, the util that lays out the disk creates the partition tables and headers, while the OS installer will create the ESP if needed. In AOS 5.1, use the two options on MiniLVM's 'System' menu to create the ESP. It's very likely that your NVME will come formatted as GPT but probably without an ESP.
should I copy those as well as the Windows partitions?
God forbid! Happily, no self-respecting tool would let you.
