Scheduling and managing events using Outlook.com calendar
Colors: some can, some can't. 8.1 gives more options than straight 8. As on Windows Phone 8, some tiles will pick up from selected color scheme, some don't.
Email: not sure as I am no longer using POP3. Surface with 8.1 includes Outlook 2013 as a desktop application. I believe you'd have control with that, but cannot verify. I regularly switch between Outlook and the built-in Email app depending on mood and use case du jour. They stay in synch, as does calendar and the web-based Outlook.com. When the Modern UI apps have the functionality I need, I m finding that I tend to gravitate to the clean-screen, no chrome option they provide. Personal preference I suppose. I have a handful of applications I still use regularly on my non-Surface laptop or my MacBook Air, but those are fewer and fewer. WebEx is the big thing missing for me on Surface RT. Except for that, I could do most of my business as well as personal work on it. I have music in Amazon cloud and can now play in desktop Explorer, though that interface is limited.
Compared to initial release, Surface has become much more useful, and I love that, all-in, it cost me a pittance including keyboard and extra charger. I can leave my house with a fully-charged Surface and Windows Phone HTC 8x as a hotspot and go all day. But it does not do everything, and You have to adapt to some things.