Here's some observations from a couple of years of use out of my TS55/CT22 in breaking down sheet goods. My general practice is to cross cut sheets to finished size with the TS55, then make rip cuts on the table saw. This method ensures me of like widths for all parts of the same width. (It's important to have a method for ensuring a square first cut, but that's another subject.)
If you layout your cross cuts first, you can nearly eliminate a need for a 3000 long rail. It's great to have a long rail, but some pre-planning is friendlier to the wallet for most situations.
A bungee from the ceiling can keep the vac hose from catching on the edge of the ply.
If you're not planning on getting a vac with the TS55, then save some $ and use a regular circular saw and a straight edge. Half the reason to have a Festool saw is the dust colection.
The foam insulation board is invaluable as a spoil board for cutting, in combination with a couple of 2x4s and a pair of saw horses.
The parallel guides are nice, but limit you to about 24" capacity. Hence they won't be helpful for repetive cross cuts that will yield cabinet sides. Your table saw will still function to make repetitive rips of like width, such as shelves, cabinets sides/tops/bottoms.
Most of the time clamps aren't needed to secure the rail to plywood.
A good sheet good optimizer will layout your parts to make cutting much more organized.
Hope this helps. Good luck with your new saw.
Joe