Yes, the weight of the bait and anything placed on the
line has an effect. Different floats can cope with different baits though,
some lighter floats will sink with even small pieces of meat, others will
actually take boilies. It is possible to fish light floats with heavier
baits than they can handle, by fishing overdepth, but this tends to have
the effect of making the bites less sensitive. If it's not too far overdepth
though, it shouldn't affect the bites too much. Also, I think there is
a cork ball attachement, which can be added to the line like shot, which
will help also with the heavier baits. It has to be a case of balance
though, otherwise you could find the bait comes up to the top.