OK, I've a few questions for you;
1. What drives are you using (exact P/N's please, as it tells me everything I need to know)?
2. What are the cable lengths used?
3. What type/s of cables are used?
4. Are there any adapters (i.e. internal to external adapters used to get the signal from an internal port to the external enclosure)?
You've lost me here.
Usually, they're expecting you to use internal ports with internal drives, which means an SFF-8087 to 4i*SAS/SATA cable (aka break-out cable). One end connects to a port on the card, and then has 4x lines with SATA/SAS connectors on the other ends (looks like a SATA cable end, but the actual cable is smaller). No difference technically though, just thinner wire is used (and the breakouts tend to have locks on them, which is a good thing).
Both internal and external cables handle 4x drives (assuming 1:1 drive/port relationship). That means 4/8/12/16 drives = 1/2/3/4/... cables on the card side, and 4/8/12/16/... on the drive side. For externals, the cable is split internally in the enclosure. It makes for a much cleaner cabling (i.e. "rat's nest" isn't as bad

).
If you're using the SFF-8088 port on the card (means SFF-8088 to SFF-8088 cable), then don't even worry about trying to figure the language out.
No, not if you use a SAS expander. That's essentially a Port Multiplier equivalent for SAS systems (they can handle SATA drives). Ultimately, it does a couple of things for you:
1. Allows the connection of more drives to the card (the 1680 series can handle up to 128 drives this way).
2. Allows for longer cable lengths (get's past the SATA limits by using SAS signals).
But if SAS expanders aren't used, then
Yes (1:1 = 1 drive per port).
There is a cost to SAS expanders however:
1. SAS expanders increase the cost of the storage system (cheap for what they do however).
2. Throughputs are limited vs. 1:1 typically (it gets detailed as to the specifics, but that's where the internal to external cables can also help you; more ports used = more bandwidth = improved throughputs).
This cable takes an internal port (card), and takes it externally to the enclosure. No adapters to mess with the signal (particularly relevant to SATA drives). The down side is, you do have to run the cables through an unused PCI bracket (no spares in the MP's case, so it means a port in this case, unless you're willing to mod the case (cut/drill sufficient holes)).