I use cjk on N800. Unfortunately, to my knowledge, there is no solution to both your requests. Back in OS2007, you can switch between built-in and matchbox keyboard. This feature is removed in OS2008. Too bad, I would also like to be able to switch between the two.

Alternative solution is to not to install matchbox, but install yet another on screen keyboard such as xvkbd. The trade-off, this is not meant for non-hildon applications. Thus, you have to run it manually. It won't automatically pop up in text entry. Search for it in this forum. Someone has ported it to the tablet.