I dunno, I flew from ATH-SIN earlier this year in the space bed and well after the new regional J and of course the A380/77W/345 product I feared the worst. However I found it comfortable enough, got a good sleep, perhaps the main limitation was reduced IFE choice. It was my first time on the 777-200ER and I had a feeling it's spacebeds were better than I remembered from the 747. Or maybe it was just that I went to Europe on the TG angled lie flat product - quite narrow - and thought the spacebed better.
Anyway the easy way to tell is to do a seat allocation on your booking (or do a dummy booking on the SQ website on your flight/day and go to seat allocation) to see what seat map it brings up. Cross check that with seat maps of 777-200 and 777-200ER and you will be able to tell exactly which aircraft is scheduled for your flight.