I do agree about Air Race. Last time I went I spend two days there during term time with absolutely no queues (we had to wait 20 minutes for more riders at G Force because they need a minimum number to send the train), but I only bothered to do Air Race once.
I don't know how much you know about the background to Drayton Manor Lordy, but there are a couple of factors behind the layout, which you may already know about. Firstly, like Alton Towers, Drayton Manor is built in the grounds of a stately home originally owned by the Peel family.
https://en.wikipedia.org/wiki/Earl_Peel
Most of the stately home was sadly demolished, but a small part remains at the front of the site by the entrance from the hotel and coach park (look out for the clock tower). The park is partly shaped by how the Peel family chose to landscape the site before a theme park was considered. I believe the lakes pre-date the park. There used to be a museum about the stately home in the zoo, next to the museum about Bryan's Penny slot machines, but last time I went to Drayton Manor it looked like it had gone.
Secondly Drayton Manor has quite strict planning issues with a housing estate running down one side of the park. That's why there are signs in Aerial Park asking people not to scream and why they had to remove Cyclone (Huss Enterprise). This also helps determine which rides can go where.
I actually like the layout of Drayton Manor as it's quirky and a bit different. I do, however, agree about the themes being a mish mash. In this respect, aside from Thomasland, things have gone backwards. Maelstrom, Storm Force 10, the miniature railway and Gallopers were all themed to a Cornish seaside town. True, Maelstrom uses a bit of 'artistic licence', but nothing wrong with that in a theme park. Pirate Cove had Pirate Adventure, a pirate ship and pirate raft themed roundabout. Action Park was Wild West themed, but started to lose the theme when Klondike Gold Mine was replaced by G Force. At one time most of the park was divided into themed areas, except Aerial Park which has always been a bit of this, a bit of that.
Drayton Manor has been innovative. Shockwave maybe dismissed a gimmick by some, but I'd rather have Shockwave than a standard Vekoma like quite a few major parks around the world added at the time. The Haunting isn't as good as Hex, but it did come first. The Wild West shoot out was the first of Britain's four shoot 'em ups to be built. Not everyone sees the point in world's first and some people will say, 'just building something that's fun'. But with Drayton Manor there was the sense of, 'what will they come up with next', and I liked that.
I think the theory behind buying up most of Zamperla's catalogue was that if you have lots of rides from a similar manufacturer they're easier to maintain because they will use similar parts. Whether it's been a rise decision I'm not sure. Since they've gone back for more Zamperla's presumably they were reasonably happy with the service. I've heard that Zamperla rides aren't always the highest quality, but I suppose you also get what you pay for and they're probably at the more affordable end of the spectrum.