Card speed really only matters when copying large files straight to or from a card itself, in normal use you'd be hard pressed to notice the difference. It does not impact the web browser in any way.

I recommend first trying the device without any swap files or other tweaks. Unlike the 770, the N800 has quite a lot (percentage wise of total memory) free working memory after booting up. If an application manages to consume all this memory, it's probably consuming memory at such a rate that it's just going to chew through whatever swap you have. This is not a good thing, it's probably better that the application just terminates instead of brining the whole device to a grinding halt because of the swapping.

Swap is a good thing if you find that you cannot have as many applications open at the same time as you would like. This isn't easy to achieve, you can open every single application that comes installed on the N800 without exhausting the memory.