DDR Memory vs. System Bus

Now, this may come off as a newb question to some of you who are more experienced with overclocking and memory timings and such, but for some strange reason the concept of DDR memory has always been kind of lost upon me. When I had to switch over from all my 100/133 SDRAM I really just knew that DDR was the new thing on all the boards.

Now, I'm not a total newb on this like I understand that like the data is transfered twice per clock so it's really like 133x2 for DDR266 memory, but like I said, it's still a bit of a mystery to me.

Right now in my machine I have a stick of PC2100 and a stick of PC2700 crucial memory. I am running an AMD AthlonXP 2800+ which touts 333mhz system bus on the box, now, am I correct in saying that I would need to run only PC2700 memory in my machine to take advantage of the 333mhz bus, and also, running higher than PC2700 would have no advantage because the bottleneck would lie at the 333mhz bus on the processor, right?

Again, I consider myself pretty computer saavy, so don't feel like you have to dumb it down for me or anything, but some of the DDR stuff is just something that never really "clicked" with me, perhaps if someone can explain the answers to those two questions I will be able to graps it. Thanks in advance!

-Cam