1. I suppose I have to install CHDK on the second card too. I can't just copy one card to other. Right?
Each needs to be prepared once to make it bootable. After that, you can copy between cards.
With old cameras like SX30 (released before 2011), there's additional complication if you use cards larger than 4 GB. These cameras require multiple partitions to boot, and your PC may only "see" one partition at a time. If this is confusing, I'd suggest using cards of 4 GB or less for these cameras.
2. After I have installed CHDK on second card, can I copy the CHDK folder from first card to the second card so the scripts & lualibrary files that I have installed on first card will be just copied to the second? (or copy everything on one card to the other). Which one will also copy the CHDK settings?
Copying the .CFG files in the CHDK folder should be enough to copy the settings, but copying the whole folder (or card) will ensure you get all the scripts and script settings too.
3. I have saved various lualibrary files on my PC in a lualibrary folder. Is it ok to copy any and all LUA files to lualibrary on any SD card even though I may not have the relevant script on that SD card? Does presence of a lua file interfere with performance of others?
No impact on performance, they will just take up a very small amount of storage on the card, probably much less than a single jpeg.
