I'm not sure about the different I/O types.
While Programming them i have never needed to worry about that.
The best way to learn about FPGA is to Download the XILINX ISE studio. In this you can do schematic capture or write your own VHDL and then simulate the results (the simulate takes a little time to get used to in order to set you test signals correctly). If you want I can post some simple VHDL code later.
When learning FPGA's the easyest is to look at a preexisting code so you can get quick reminders about signals vs variables and their different formats. Other things such as I/O, type, size, and header info can be done with the wizard or copied and modified easily from preexisting code.
A quick google search gave me http://www.easyfpga.com/ez2susb_features.htm
which has reasonably priced devel boards. The only problem is there is no restore EEPROM so it will need to be reprogrammed on every start up.
If your designs are relatively small there are Good CPLD devel boards that are nonvolatile.