Wow, a lot of fruit being thrown in this basket! Too many apples and oranges in this discussion. I read through everything but don't seem to understand the goal- better dust collection is way too broad, especially when talking about a table saw! Are your goals (1) improve dust collection around the blade, i.e. reduce the amount of fine and coarse dust thrown off the blade, and (2) improve collection in the cabinet, i.e. reduce the amount of dust collecting in the cabinet (and possibly escaping from the cabinet)?
A quick review- dust collectors need both SP (static pressure or simply suction) and CFM to operate properly. SP to overcome friction loses created by ducting/fittings/duct diameter and CFM to move a large volume of air. You can have high SP at zero CFM (the old vacuum cleaner commercial where they pick up a bowling ball)- doesn't do much good for wood dust collection more than an inch or so from the intake. You can have high CFM but relatively low SP like in an HVAC system, but it won't pick up heavy dust. Both attributes can be plotted on a graph called a fan curve that is unique to each motor/blower unit. The point on the curve where your dust collector operates can vary due to ducting, but it is always along that curve. If you have just a short wide pipe running into the blower, you'll have the system’s max CFM but its lowest SP. If you block off most the pipe the SP will rise to its max but the CFM will be almost nil.
The reasons a dust collector needs SP is to be able to pick up and collect dust and chips. The reason it needs high CFM is because while dust is typically generated from a point source on most machines, it can quickly spread out in all directions, including in the direction of the operator. You must collect from all directions- compare the volume of dust-laden air instantly generated at the source to the much larger volume of dust laden air just a few seconds later!! That requires a lot of CFM.
Let's talk about (1) first. If you do the math, a table saw spinning a 10” blade at somewhere around 5500 rpm (typical for a TS) potentially throws dust and chips from blade tips AND gullets at the operator at somewhere around 160 mph (check my math)! No typical dust collector mounted to the cabinet will provide enough SP or CFM at the blade opening to stop this. You need some sort of over-blade shroud to capture the dust and kill the kinetic energy of the dust until it has slowed sufficiently or is stationary so it can be picked up. If the hose running to the shroud is small (e.g. 2.5” or smaller) you’ll need something, like a shopvac, with high SP to collect the dust. Two issues with shrouds- like the cabinet, they must have a source of make-up air- under the lip or through a skirt (like a CNC router skirt) and there are many operations where it just can’t be used effectively.
As others have mentioned you must have the same square inches of opening in the cabinet for make-up air as you do at the dust collection port. Also, remember the area of small openings don’t add linearly due to friction loss, so you actually need more cabinet inlet area than the dust port. If you don’t, you’ll be killing CFM. To ensure dust doesn’t collect in the cabinet, just make the floor of the cabinet slope relatively steeply towards a dust port on a side or preferably at the bottom.
One more comment- you aren't doing yourself a favor by using "low velocity" wyes on your ducting instead of standard wye fittings. They are cheaper, but low velocity wyes generate turbulence that raise SP at the expense of CFM.