As others, especially Tom Bellemare have stated, the Domino500 only accepts the 27mm hose, which is more than enough because the Domino dust is as fine as from a sander. However, with the Domino the flexibility of the hose is very important. So by all means keep the 27mm AS hose which came with your CT26.
I only use my OF1400 and OF2200 for routing jobs which produce not only dust but near planer-size chips. I bought my first OF2200 before the OF1400 was available and always only used it with the stiffer 36mm hose. With practice you get used to doing so. When I finally bought the OF1400 it felt natural for me using the 36mm hose.
By the way, I have only used the 36mm hose with my TS55 and TS75. That does improve dust collection. Think about it, those saws are moving in a straight line on a guide rail. What you try to avoid is snagging the hose on the rail.
Guess what? The stiffer 36mm hose is far less prone to snagging on the rail. So that is a win-win.
The jig saws, the MFK700 and the OF1010 only accept the 27mm hose, but Tom B makes a marvelous adapter which plugs into a 36mm hose. Really kool.
All the Festool sanders need the 27mm hose and you should be within reach of the suction control when sanding because setting the suction is the secret to best sanding.