it really depends how far you would want to cg someone to. It sort of dependent on how high you want to CG someone. Bthrow > Bthrow buffered in theory is the fastest standing alone. However, you have to factor in move decay. Over 10 throws, you'll gain back a throw of damage percentage, which would then mean that you'll pick up a throw in overall time speed. It would then depend on which character you are bthrowing because the length in time in relation to the constant time of fthrow varies.
So the longer you CG someone, the better your version becomes up until a cycle of 10 throws at which it is constantly better by 5 or 6%. But at lower percents, it's probably better to for speed purposes bthrow > bthrow. I think in terms of spacing however, bthrow > fthrow is the BEST cg. But that last one is opinion.
But yes, you should be able to buffer this. The only throw that can't be true buffered in a cg is the dthrow on some characters because you need to shield buffer.