To answer your initial questions, yes that's right :) 1/4" is the side of the drive on the wrench itself (they go 1/4", 3/8", 1/2" etc) and therefore any sockets/adaptor you get, need to be 1/4" drive.
As for whether you need a torque wrench, I know that some people with expensive bikes use torque wrenches to get the correct torque on bolts, etc. I've not heard of that for screws, (and given you're buying a screwdrive bit set maybe that's all you'll be using it for) so if that's the case you could save yourself some money with a simple wrench, but if a torque wrench is what you need, get stuck in!
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