What device do you need?
The service is available across Apple hardware. So you need a Mac, iPhone, iPod touch, iPad or Apple TV. These will need to be running iOS / iPadOS / tvOS 13 or related macOS Catalina.
It is reasonable to assume that newer devices may be better able to cope with more demanding games, but Apple did not say that older devices will not work with Apple TV.
The last thing you need is a permanent Internet connection. Games can be used offline once downloaded; the exception is Apple TV, which has various weird restrictions on download size on this hardware.
What controller do you need to play Apple Arcade?
Yes, not at all. As far as we know, all Apple Arcade games can be used directly and are compatible with Apple's hardware. So you will be able to use Mac input devices, iOS touch screen and Apple TV Siri Remote.
The last one may make you realize that although you technically don't need a controller, you will want one. Fortunately, if you can run Apple Arcade, it will work with PS4 or Xbox One controllers regardless of which version you are running. And, if you come across an old MFi controller like SteelSeries Nimbus, that's fine too.
How much does Apple Arcade cost?
Apple Arcade is a subscription. It’ll cost £4.99 per month, and your subscription will work with Family Sharing (up to six users) for no extra outlay. Prior to opening your wallet, you’ll get a one-month free trial. Note that Apple Arcade games have no ads and no in-game purchases.
As for when, the service will launch in over 150 countries and regions, and gradually roll out to Apple’s various devices. On 19 September, it comes to iOS (iPhone/iPod touch). On 30 September, iPadOS and tvOS get in on the act. The Mac will get Apple Arcade some time in October, when macOS Catalina finally yomps on in.