For the record this is what I ended up with after about 2 or 3 ISO’s as first off I tried the Live CD, but missed the bit about that not being used for installing. Ended up using the offline snapshot image.
Had to go through the installer a few times to try & get it right as the first time it tried to give me a small boot efi. Eventually it seemed to default to 1gb but I couldn’t see anywhere or work out how to enlarge that - so I ran with it, not wanting to go through the whole thing again. I nearly fell into the systemd trap but realised at the last moment (although that may have been OK) & then switched to my preferred GRUB2 via thje left hand menu.
So in the end this is what I ended up with - the first disk being the Windows drive supplied with the PC & the second being the Tumbleweed one as discussed above. It also proposed I think a 16gb swap file maybe(?), although again I though I might have gone bigger on that too, but same comment about not being able to work out how to change the proposal & just wanting to get it done applied.
NAME FSTYPE FSVER LABEL UUID FSAVAIL FSUSE% MOUNTPOINTS
nvme1n1
│
├─nvme1n1p1
│ vfat FAT32 SYSTEM 6CDE-8B57
├─nvme1n1p2
│
├─nvme1n1p3
│ ntfs Recovery 4CB2DEEAB2DED812
└─nvme1n1p4
ntfs 6EF2E221F2E1ECF1
nvme0n1
│
├─nvme0n1p1
│ vfat FAT32 B25A-50C7 1021.6M 0% /boot/efi
└─nvme0n1p2
│ LVM2_m LVM2 XhOlrL-HXi9-1wYM-3mb8-xMaj-t8Vf-2MMbzk
├─system-swap
│ swap 1 c0f64bdf-fb83-4716-945c-20a6ae522544 [SWAP]
└─system-root
btrfs 22d00a64-814a-4124-ad9f-33ce64307c77 897.2G 1% /var
/home
/root
/srv
/usr/local
/opt
/.snapshots