Each of us has to develop work methods that are effective for us. I cannot say what is going to be best for you. I can only share my experience. I have been woodworking since 1937 and concentrating on building cabinets since the summer of 1946, when consumer circular saws and 4x8 sheets of plywood became available following the war.
The downside to breaking down full sheets on a table saw is that you need to push the sheet through the blade. This is less effort once the sheet is reduced in weight. A consequence of pushing sheets through a table saw is that one side will be in contact with the table, so should something hard stick to the table scratches can happen. Even with an expensive slider saw, the part against the rip fence is still resting on the stationary table. In the cross-cutting mode with a typical table saw the accuracy of the angle is based on the protractor of the miter gauge.
Going back to 1946 my method has been to start with a sacrificial surface made from a full sheet of plywood. I take my time accurately trimming one of the long factory edges so it is smooth and straight. From that clean edge I carefully render the opposite long edge smooth and parallel. Next I turn my attention to cutting each short edge at right angles to the clean long edges.
An old principle of geometry is that when you place a suspect framing square along a straight side, then draw a line, flip the device and draw another line. If the lines over-lap, that device is a perfect right angle. Obviously that flipping must happen near the center of the sheet. Once satisfied that the line is a right angle to the clean long sides, then measure the same distance from both ends of the line toward a short side. Connect those marks with a continuous line. Double check that line to be sure it is a right angle to the long sides. Carefully trim to that line. Now do the same at the far end of the sheet. Double check all four corners.
Now your sacrificial sheet is also your master for squaring all actual parts you will make from subsequent sheets. Just be sure as you cut all that subsequent sheet material you only nick the sacrificial surface. Cut through it and you get to start the smoothing of edges and squaring all over again.
Normally the first step breaking down a sheet is to clean one long edge, removing the absolute minimum of material. I like to take just enough I leave a thin strip as waste, since if the off-side of the blade is not still cutting the saw can be drawn off line.
This is where the Festool system is so efficient. The ideal rail to make the long cuts is the 3000mm (118") guide rail. That is long enough you can spread the Festool parallel guide enough it does not interfere with making the first clean up cut. Now you turn the rail around, so that the piece you are cutting is under the rail. Adjust the guide on the rail so that you have about a finger width of play. The reference points on the guide will still touch the clean edge. Of course previously you calibrated your parallel guides per the instructions. If those are not clear, use the supplemental instructions and watch one of many instructional videos. Better yet, either participate in a Festool End User Class or get a trained pal to coach you.
The idea is to use the long guide rail and the parallel guide to break down the full sheet into narrow strips of 24" or less. Those can accurately be cross-cut using the MFT/3 set. However, since your sacrificial surface has all of its corners right angles, you can confidently reference that to establish right angles when cross-cutting those narrow strips.
In actual cabinet making you will find it is rare to need to cross-cut a full 48" Remember, without an external reference the Festool Parallel Guide does not ensure right angles. That is the beauty of taking the trouble to create your sacrificial surface with all accurate right angles. Position the work in contact with a clean edge, and they you can reference from the appropriate corner. The Festool 1900mm (75") Guide Rail is ideal for use with the parallel guide for making 48" cuts. The 1400mm (55") rail is easier to carry from site to site and very handy when making cuts up to 49" with a TS55 and without the parallel guide. As I say, in the real world of cabinet making most cuts over 40" are made in the ripping mode.
Before I built my current custom cabinet shop I had learned the virtues and limitations of the CNC Pressure Beam Saw. If you have not seen one of these in action, think of Festool guide rails and the TS75 on steroids. The pressure beams are like 4 guide rails, 2 each on the top and bottom surface of the material being cut. Each pair of rails is almost touching the blade on both sides. The pressure is adjustable, but enough to minimize tear out. The saw is pulled through the work smoothly at an adjustable rate from below and the saw has a scoring blade which can be programed to either score or not the work. This cutting goes very rapidly, almost always starting with a clean up pass along the long side. So, it is line a CNC parallel guide, turning the sheet into strips with accurate parallel sides. The beauty of the beam saw is that both sides of the kerf are free of tear-out.
Once the sheet is broken down into strips, the entire stack is rotated so that one-by-one those strips are accurately cross-cut at right angles. With an experienced mill hand it takes less than 90 seconds to break down a 4x10 sheet into perfect cabinet parts.
Yes, CNC beam saws are expensive and require dedicated shop space a bit larger than a sliding table saw. Until you have a production volume to justify a beam saw, take the trouble to become at one with a sacrificial surface, your Festool track plunge saw, your guide rails and the Parallel Guide. Let me add in conclusion that the Extension accessory is worth the price, even if you seldom need to cut extra narrow strips. The weight of the extensions helps hold the guide rail in place, almost always avoiding the need to clamp the guide rail.
My shop also has 2 CNC nested routers and a CNC sliding table saw. The beam saw only makes right angles. It cannot make a bevel or miter cut. Sure the sliding table saw can do the bevels and miters very accurately, but doing so is labor intensive. So, I have a 4x18' cutting table with a sacrificial surface, drilled similar to an MFT with 20mm holes on 96mm centers. Those hole can be used as efficient references for right angles, as well as some other angles of miters.