I believe SwiftKey is a subsidiary of Microsoft and Gboard is Google's. Their differences are quite noticeable after you try both. In my opinion, SwiftKey is better, especially in terms of predictions and general functionality. It is eerily accurate. Personally though, I use Fleksy.Both keyboards are identical because they both come from Google.
Basically this poll is Google vs Microsoft... I will try Swiftkey soonSwiftkey it's owned by Microsoft and Microsoft don't buy that keyboard maker for their keyboard but for their AI(artificial intelligence), privacy is not the best for both apps(swiftkey or gboard - both collect data)
SwiftKey - Wikipedia
Microsoft is bringing its SwiftKey keyboard to Windows 10
Ah, I think you are talking about writing in two languages with the same basic character set, such as English and Spanish.You have english(for exemple) as default, add chinese for exemple and thats it. Swiftkey will be able to write in what language you want.
They say on blog.swiftkey.com that you can do 3 languages at the same time, and if they have different character sets:From what i know, SwiftKey allows you to use up to 5 languages simultaneously.