What's the functional difference between projects that use these two icons in Visual Studio? Are there limitations to one type of website vs the other?
One of my organization's older websites has this:
The newer websites have this:
Right of the bat, I noticed there is no References list in the solution explorer for the older website. Additionally, I'm struggling to have standalone .cs files be usable elsewhere in the project with using statements.
It seems your older website is built on ASP.NET Empty Website template, while the new one uses Webforms project template. So in the second case you would have a basic setup for the project including references, defined structure, starting sites etc. You could read more below about the differences:
ASP.NET Web Site or ASP.NET Web Application?
As you miss references, it might not be possible to do certain imports, but in either case you can add References from menu Project ... Add Reference
https://msdn.microsoft.com/en-us/library/7314433t%28v=vs.90%29.aspx
