Does your Denon have hdmi inputs? If so you should plug your Vero into that and turn on passthrough in the Denon’s Video settings. This way the audio will automatically switch from the AVR to the TV depending on if it is turned on, and your audio delay issue should also disappear.
With passthrough turned on in the Denon it just forwards the hdmi signal to the TV when it is off so your TV acts like the AVR is not there in the first place. In mine you can set it to forward either the last source or a specific one. What your TV does depends on if your using CEC and how it is configured. With CEC turned off you would have to manually mute the TV like you do now when you are using the AVR. If you use CEC then you will probably have to play with it to figure out what your TV can do.
How well this works depends on your equipment but I did test it on my 2019 LG TV and Denon AVR. With my TV set to use ARC for audio and to not control power state of AVR, and the Denon set to passthrough I have full audio/video in sync with the AVR on or off. When the AVR is off the TV’s CEC knows that it doesn’t have an ARC connection so it switches to the internal speakers. If I turn the AVR on the TV automatically switches over to ARC (which turns off the internal speakers) and outputs audio from my stereo.