The feature is in the Functions set up, you can select next bar or instantly - see below, also to keep the chord going you need to activate LH Hold.
The following relates to my Tyros4. I suspect that things are just the same on other Yamaha arrangers too.
The chord always changes immediately when a new chord is detected, wherever this may be in the bar. This is the same whatever fingering type you use. I am not aware of any setting to change this!
I assume that the function setting that Bill referred to is 'OTS LINK TIMING', but this only affects when OTS changes occur when triggered by changing the style section with the 'OTS Link' button on. It does not affect the timing of chord or style section changes!
The 'LEFT HOLD' button button only relates to the 'LEFT' main voice part, and has no effect on the style accompaniment at all! Once started, the style accompaniment will play continuously until you stop it by some means, tracking chord changes in real time, whether the 'LEFT HOLD' button is on or off!
The style section changes at the beginning of the next bar, unless you select the new section while the beat counter is still showing '1', whereby it changes immediately! This is also the case if the style section is changed by a registration.
At normal tempos, it may not be easy to pinpoint exactly when changes actually occur after pressing a button, so slowing the style down can make things easier to see. You can check it out for yourself if you select a style, drop the tempo right down to 30 or so, turn on the 'OTS LINK' button, and start the style playing.
This makes it much easier to see and follow the time of chord changes, OTS changes and style section changes. I also turn off the 'AUTO FILL' button to avoid confusion when checking the style section changes.
Watch the style section buttons, the OTS buttons, and the Chord indicator and Beat indicator on the Main display to see what happens when you play different chords and change style sections at different points within a bar.
Regarding what you have seen in YouTube videos, bear in mind that the sound is not always perfectly synchronised with the video! Perhaps that is what you have seen?