hello mate. with regards to chosing either nft or bubbler's, you won't fit a gt100 in 1m2, it's 1200mm x 1060mm x 230mm. I've tried both and personally i prefer nft because the res is separate from the root mass, which makes cleaning and ph and ec testing a lot easier.
i bought my ph and ec pens of ebay, about £12 each but be warned, i bought one and it was crap. the two i have now are absolutely spot on.
calibration is making sure the readings on the pens are accurate. this is done by putting the pen in a special soloution at and exact ph/ec, and adjusting the pen so it reads correctly.
Bob