It really seems to differ based on location. I have stayed multiple times at the voco Grand Central in Glasgow, and it's been quite nice. Full service, bathrobes and slippers, towel warmers in bathrooms, free upgrades (as Plat and Diamond). Comfortable beds and nice amenities. The one in Edinburgh looks nice and the one in London that just opened seems to parallel at least some of Glasgow. Someone posted last night about the Leicester voco, and that didn't look like a hotel I'd try. That is likely a management thing, not a brand thing.
There's a voco now in Chicago, and it is very nice, shares a space with a Holiday Inn, and the voco remodel got the top floors.

It's not like a Tru at all, though I hear some folks think it is more a budget brand? I like them. They aren't the Conrad or Waldorf Astoria, but they are not HIX or Tru. The Voco Bilbao looks more budget-y in appearance with the small, basic rooms, but I would still expect elevated service. Perhaps someone else has stayed there and can chime in.