The arm rests are not just fixed along with a mini drinks tray welded into place, but there is quite a distance between seats. You're not going to be rubbing up against your neighbour but that's true for all WTP seats. I don't think there's a clear set of good versus bad here, it's more about whether you want to be window or aisle. On the A350 there is no WC or galley proximity issues.

The exception will be the first row of the WTP cabin, row 20, however it's the same for all of BA's WTP cabins. This has a decent amount of knee room in front of you, such that people can move from the window and middle seats to the aisle without greatly disturbing the aisle passenger. But because the IFE screen is stored in the seat sides, this means the seat is narrower than other seats, and you lose easy access to the seat front pocket as well as the front drinks holder. There is also slightly less leg room, given that legs go under the seat in front elsewhere, but probably most people won't notice this, it's all about optics.