Well, Cliffs of Dover is to be frank in a really sorry state.
At its core are brilliant assets and concept, but riddled by engine performance issues and tons of bugs, and as a result I don't understand any other reason for its release than Ubisoft pulling the funding for continued developement, and the team was forced to rush it into a state where it barely passed Ubisoft's QA and was approved for publishing.
The game shouldn't have been released yet, and to be honest I have to wonder why exactly is the engine so atrociously poor. I mean, at low settings it doesn't look better than IL-2 Sturmovik, but manages to maybe achieve 5% of the playability of IL-2 1946.
If you don't mind buying a game essentially in beta (or even alpha) testing phase, then get it, if not for anything else you'll have an unforgettable experience trying to play the game. If you have a really modern rig you MAY have adequate performance... sometimes... but seriously, I have to still wonder where all the seven years were used on.
It's possible that they are trying to simulate way too many things for one frame and end up reducing performance as the game feverishly tries to calculate all the stuff it's supposed to, and refuses to advance to next frame before all is accounted for... and really, this isn't a good approach for a flight simulator. A flight simulator needs, first and foremost, good frame rates for playability (I would say minimum of 30 FPS, preferably at least 60 FPS) and other things scalable so that this frame rate can be achieved on minimum specification of hardware.
Well, I hope they fix the game even if it takes an engine rewrite, because the graphical assets are really something. Meanwhile, IL-2 1946 will remain the premier product on WW2 combat, if not for any other reason that Cliffs of Dover remains unplayable for most of its target demographics.