It’s not good or bad to have an independent chair at your viva.
Independent chairs are not examiners. They’re often a senior member of staff from your institution who is mostly acting as an observer. In your experience of the viva, it will be like having a teeny-tiny audience making notes. They won’t ask you any questions about your work.
They might ask examiners to move on from a topic if they think enough time has been spent. They might ask if anyone wants to take a break. But really their job is to observe and ensure that your viva is a fair process.
Not every viva has an independent chair. They’re sometimes used if an examiner has less experience. They’re sometimes used as a kind of quality control, checking that vivas are held in a fair way. Some departments or universities always use independent chairs because that’s what their regulations say. An internal examiner can take on some of these responsibilities, which is why independent chairs are not a universal part of the viva experience in the UK.
The best thing any candidate can do is find out in advance what the situation might be for their viva. It’s not good or bad for you: it’s just something to be aware of and something to consider as you prepare for your viva.