I've been looking for something similar, but haven't found any plugins that let you view the parameters of functions.
If I can't remember the functions params I run CTRL+R (Goto -> Goto Symbol), and it lets me search through all functions I've written.
About the string and table libraries; the closest I've found is
Lua Love plugin. I haven't played with it much, but it seems to have most functions in there. Don't forget to change language file to "Lua (Love)", but I some functions work with ESOLua.
If all else fails, you can always define your own snippets.
*Edit: btw, I made snippets for
LibAddonMenu for Sublime, located here:
https://github.com/Saucyboy/sublime-ESO-LibAddonMenu