If what you are using works well and has no performance loss. Then stick with it.
Keep the BT in reserve and if you ever suspect you have an issue then you can drop that in as a control for fault finding and then ring customer service if inconclusive.
The control you get from your own equipment is worth it.
Yeah I think this was my general conclusion. I was a bit worried as to whether the Draytek would even work but I think it has a Gb WAN port that should work plugged in to the ONT. We don't even own any wifi 6 devices so I'm not going to be losing anything in terms of speed for now.
If what you are using works well and has no performance loss. Then stick with it.
Keep the BT in reserve and if you ever suspect you have an issue then you can drop that in as a control for fault finding and then ring customer service if inconclusive.
The control you get from your own equipment is worth it.