My answer for how long this can be in a virtual interview differs from an actual interview scenario, the reason being that it's harder to pick up on social cues about how your answer is being perceived in a virtual interview as you're generally looking into the camera while you're speaking. With this in mind, keeping it to a minute or so should be good.
Although, my greatest tip would be to instead focus on making sure that your answers are sufficiently detailed by not going too far into the nitty gritties and at the same time ensuring that your answer isn't sparse either. Doing so will not only keep you within the timeframe you'd like to limit yourself to but will also ensure that you're keeping your interviewers engaged.
The structure I'd recommend to use while prepping for your competency questions is either STAR or briefly state the competency ➡️ walk the interviewer through your actions/thought process that demonstrated your competency ➡️ elaborate on the impact of you applying/developing this competency.
