For the differences between the Q/EQ/EBQ, the 'Q' is single speed, no electronics; the 'EQ' is variable speed with electronics e.g. soft start, constant speed, load and temperature cut-out etc… and the 'EBQ' is the same but with an electronic brake.
You can check the differences between the current models (TS55 and TS75) on Festool.co.uk here - and you can download brochures and operating instructions from Festool.co.uk as well.