Thanks for replies so far
Ok, referring to Inn's overview (good job!

)
1) looking at the lines where black plays dxc4 & follows up with b5; wouldnt this be considered a QGA

That sure looks like playing a QGA in typical KG style!! So slav & semi slav can be both a QGA or a QGD system, yes?
2) Given that there are lines where white allows dxc4 & some where white disallows the said move, that means the c4 pawn isnt really a gambit in the literal sense isnt it? It only becomes one when white allows it to be taken. Contrast to KG where it is defintely up for grabs.
3) In terms of active piece play and a freedom of movement, how do these slavs/semi-slavs compare to the semi-tarrasch which ive used from time to time? Would it suit me as a sharpish positional player? Any particular variation to recommend? Or I'm just better off with my semi tarraschs & KIDs
4) Ive always opened with 1...ktf6 against 1.d4, as it gives me the flexibility of choice betn a semi-tarrasch, Cambridge Springs (easily avoided with 3...a3) or an Indian/Benoni-whatever the moods decide. How feasible is it to strive for a semi-slav by 1st playing 1...ktf6, or its just best to play 1...d5?
Again, my apologies if these questions sound rather silly.

Thanks