Yes, Canon indicates that this unit should be compatible with your 7D.
I am a near sight user. Do I need to choose "+" or "-" for using?
You need to use - (negative).
Near sighted users require a "-" adjustment, farsighted users would require a "+" adjustment.
Does it fit a 70D also?
-- EOS-1D Mark IV Body
-- EOS 6D Body
-- EOS 5D Mark III Body Refurbished
-- EOS-1D Mark III
-- EOS 5D Mark III Body
-- EOS-1D X Body Refurbished
-- EOS 7D EF-S 18-135mm IS Lens Kit
-- EOS 70D EF-S 18-55mm IS STM Lens Kit Refurbished
-- EOS 5D Mark III EF 24-105mm f/4L IS USM Lens Kit
-- EOS 7D EF 28-135mm IS Lens Kit
-- EOS 5D Mark III EF 24-70mm f/4L IS USM Lens Kit
-- EOS 7D Body
-- EOS-1D Mark IV Body Refurbished
-- EOS-1Ds Mark III
-- EOS 70D EF-S 18-55mm IS STM Kit
-- EOS-1D X Body