Regarding apps - you can find them for pretty much anything. Often it will just be a better optimised version of their webpage e.g. Facebook & Twitter. Sometimes they are specific, for example guitar tuning software, tv guides, games, bet calculators, BMI calculators etc. etc.
The speed of the phone doesn't just affect apps running, the whole running environment could be slicker or slower moving between screens or loading web pages etc. Assume if it isn't negatively mentioned in reviews then the phone runs perfectly well.
As arriba says, look at some reviews - this site is also a good one:
http://www.techradar.com/search?searchTerm=HuaweiDon't forget things like the camera, internal storage space etc. It sounds like if you just want web browsing and emails to get a phone with a decent screen and one that runs smoothly. The S2 is still a really good spec phone, but it's by no means near the quickest ones these days.