Here is an overview of the iOS version, via CD Projekt RED:
GWENT: The Witcher Card Game on iOS combines the full feature set of the PC version with controls re-imagined for the touch interface. Progress and purchases are shared between iOS and PC (using GOG account), so players can easily switch platforms anytime. Additionally, on the most powerful iOS devices, GWENT: The Witcher Card Game has built-in 4K textures.
Supported devices include iPhone 6S or newer (including iPhone 11), iPad Mini 4 and newer, iPad 5th generation and newer, iPad Air 2, and newer and all iPad Pro devices.
More information about the iOS version will be announced this weekend during the GWENT Challenger, a tournament with a $100,000 prize pool. It will be live streamed on Twitch on September 14 and 15 starting at 7:00 a.m. PT / 10:00 a.m. ET each day.
GWENT: The Witcher Card Game is currently available for PlayStation 4, Xbox One, and PC.