I believe you are asking about the individual driver and passenger bed sizes. As you know, the passenger side is longer. Both are the same width. And that width is the widest that I am aware of on the market. While it makes passage from front to rear of the coach narrower than other Class B twin bed setups, my wife and I enjoy the extra width to sleep on.
In any case, these are custom size single beds. We use sheet covers made for regular single beds and simply tuck excess under. The Froli "springs" do fairly well at keeping the sheets positioned. In fact the Froli System and the provided mattress-cushion work so well, we have no thoughts of ever adding and additional cushion. Every other bed cushion we have seen or tried in other RV's have never been comfortable to us as they come from the RV factory.
But of course adding memory foam may enhance nicely for you. I am sure they will help fill out single sheets to fit better than what we do. The ultimate would be to have custom sheeting made up for each bed. My wife added thatt maybe some kid size sheets might fit better. I am not sure what the definition of that means.
As for adding in the center section to make one large bed, we found we never do that. While our preference is to sleep together, when we travel, being apart by mere inches is fine. Besides, we have so much fun every waking hour with our 59K, by the time we hit the hay, we sleep like rocks on the factory mattresses and Froli System. We are truly Happy Campers.
If your new to RV'ing, I highly recommend your first two overnights are clise to home single or maybe 2 night test trips. Get the Truma Combi heater operation down pat. With hot water, take a shower so you get that routine down. Like where u set your towel, clothes, bar of soap and shampoo. Closing blinds/window covers. Is tge lighting at the excellent mirror good enough? The lighting at the mirror fir us wasn't so I added lighting myself later, for example.
Getting an idea on water usage. Grey and black tank operation by first trip to a dump facility. Even if u have previous experience, the first one or two quicky trips help figure out Travato routine. And capacities of tanks-usage. Little things to smooth out in your test trip experiences to make the first real trip all fun.