It can do everything RSD 2.5 can do and more.
You do not have to use the design layout grid option. You can just make your website as in RSD 2.5. The only difference is that CSS Grid no longer has the row and column span options. You just use flex which essentially does the same thing way better.
If you choose to use the grid layout option you can do so for the whole web page or for just a section of the webpage.
According to Bob they are working on a fallback feature for old web browsers that do not understand grid layouts. Actually Firefox in Windows XP has grid and if you turn on experimental features in the last Chrome Browser for Windows XP it handles grid layout also. I have already experimented with adding the fallback in after exporting the project and its works flawlessly. If you have a older web browser it will fallback to the flex designed layout and if you have a newer web browser it will show the new grid layout.
But there are some great additional features in this program like the addition of pseudo classes and dynamic classes that make this design program "cutting edge".
The new layout of the entire program is much more intuitive also and saves a lot of extra clicks one has to perform when in RSD 2.5.
I am still scratching the surface but really excited about this complete advanced website building program !
The thing I love about what Coffecup has done with CSS Grid is that it provides you with a visual layout between your different breakpoints BEFORE you start adding your elements. Once you have your layout made....you just tell the elements where to go in the grid. Awesome !