You won’t get to fully decide when and where and how your viva takes place. You’ll be asked when you’re free and what your preferences might be. By then you’ll know who will be involved and you’ll know what it will all be about: your thesis will be finished and you’ll be in the process of getting ready.
The final logistical details of the viva are when and where.
When you know the time and the place just consider what else you need to do. Do you need to go and check the room out at your university? Or do you need to think about where will be best at home? Do you need to decide how you will get there on the day? Or do you need to practise using whatever video platform the viva will use?
When the time and place are confirmed, simply think about what that means for you. What else do you need to check or do?