Can the 60mm deep drain be placed snugly against the walls, with the tile backer board sitting on top of the flange. Can the drain be set on a slightly lower screed bed along the width and length of the drain, can this be an alternative to the legs which would protrude and not allow the drain to sit against the walls
Drain is surrounded by 20 mm wide flange. If your tile backing boards are 20 mm thick, then yes, you should be able to fit the drain right against the wall and fit the backing boards in between the wall and drain grate. In addition we are able to manufacture custom drain with upstand flange, however unlike standard products available on our website it can take 6-10 business days to have it manufactured and delivered. Let me know if you're interested in such solution.
Regarding feet - they are not attached by default and are especially useful for timber flooring. If you don't require you can use for instance some cement to position them in the right spot and then proceed to screeding.
I am happy to help if you have any questions.
Kind regards David