so yes the Range limit is for the long Range Disadvantage,
so the limit is for the weapons is as follows
Dart - out to 20 feet
Short bow - out to 80 feet
Sling - out to 30 feet
Long bow - out to 150 feet
Ballista - out to 120 feet
Cannon - out to 600 feet
Mangonel - out to 200 feet
Trebuchet - out to 300 feet
so this is also true when used together
True Strike - Advantage on next attack or Help - Advantage on next attack or Greater Invisible
Sharpshooter - attacking at long Range doesn't impose disadvantage on your ranged weapons attack rolls
so the new Sneak Attack damage Ranges are:
Dart - out to 60 feet
Short bow - out to 320 feet
Sling - out to 120 feet
Long bow - out to 600 feet
Ballista - out to 480 feet
Cannon - out to 2400 feet
Mangonel - out to 800 feet
Trebuchet - out to 1200 feet
and at these distances my Halfling Assassin (Greater Invisible) could wait for the King of a castle or Dragon or Captain of a Ship to come into view, shoot, fire or what ever the terms is for the weapon, get surprise, and get auto Critical and at 17 level double the damage, add some poison bolts or mercury in the cannon shot
then move to the next weapon that was readied by the crew and do it again
It reads for the weapons; "One Target" be it a Ship or a Creature
This is All RAW (and Damn to "RACS, Rules As Common Sense)