SoftHead lures are generally used as teasers for both regular trolling and Bait 'n Switch fishing. They can also be trolled as lures with a hook set.
Large soft head lures are preferred over regular hard resin heads for a couple or reasons - they feel more life like to an angry marlin trying to eat them and this will keep the fish in the spread longer giving the anglers more time to execute the bait and switch hook up. Also when the lure arrives back in the boat it's soft head will not damage either the boat or the crew when it often slings back in at high speeds!
Large SoftHeads make great bridge teasers too, just by themselves or at the end of a squid chain, they can be retrieved out of the water and left swinging around without fear of them hitting and damaging the boat.
Smaller soft head lures can be used equally efficiently at slow speeds when trolling baits at under 6 knots.