Reading this thread prompted me to try turning of the TCS.
The last few days driving around my neighbourhood with it off, it was hard to tell if anything was different. I haven't driven enough to determine if it affects gas mileage.
However, I did discover one unexpected thing yesterday: I went on the highway for a 10 mile run, and found out that the cruise control will not work with the TCS deactivated. It failed to engage, and I got a warning message on the dash. I activated the TCS, and the cruise worked. As soon as I hit the TCS button to turn it off, the cruise disengaged.
So much for that experiment.
That's interesting. I did a word search on "TCS" in the PDF format of the 2020 North America manual (79 instances) to see what TCF OFF might affect. There's no mention of cruise. Did you try to engage radar cruise, conventional cruise, both? I've not yet tried it myself.
Here are the TCS OFF affects (or possible affects) per the 2020 manual. The manual makes no differentiations between normally aspirated vs. turbo or AWD vs. FWD or variation by country. I can't speak to other years. These references are sprinkled throughout the manual.
Lane Keeping / Lane Departure
Per page 4-165, these systems go on "stand-by" with TCS OFF. In other words, they don't activate as is the case when you brake or make a turn or jerk the wheel, among other operations.
Stability Control / ABS
It is not clear from the manual whether stability control or traction control are affected with TCF OFF. The manual states at page 4-110:
"The Dynamic Stability Control (DSC) automatically controls braking and engine torque
in conjunction with systems such as ABS and TCS to help control side slip when driving on slippery surfaces, or during sudden or evasive maneuvering," That's understandable given what these various systems do.
On the one hand, nowhere does it say that stability control or ABS are deactivated or affected with TCF OFF. However, that "conjunction with" raises the possibility that behavior of the other systems is altered.
In the complex interconnectedness of this stuff, an alteration of engine torque and between different years / engines / drive systems / software versions might account for differing experiences of driving dynamics with TCF OFF as reported here even in normal driving. Personally, doing only about 25 miles of TCS OFF driving so far, I detect no difference in driving dynamics. My book is till open on gas mileage.
Some vehicles such as my Sienna will deactivate stability control when turning off TCS. It's hard to tell the affect in CX-5s in normal driving and it would be dangerous to test the difference between TCS OFF vs. on in stability control except on a closed track in aggressive maneuvers.
Manual Shift Mode
Aggressive manual shift drivers who use TCF OFF should refer to the manual shift section of their manual. It starts on page 4-67 for 2020. System overrides of driver inputs are cancelled or altered when flooring or redlining with TCF OFF.