Both spots above are solid. A few practical notes for sit-on-top launches at low tide specifically:
The Bravos Way ramp is probably your best low-tide option — sandy bottom means you won't sink knee-deep getting back in. Worth checking the launch angle at minus tides though; some concrete ramps end before the water does.
The Hernando Beach Marina day-use area is worth the $5 if you're going out for more than a few hours. The protected water near the marina tends to have less wind chop on afternoon returns, which matters on a sit-on-top.
One thing neither answer mentions: the channels off Hernando Beach can have meaningful current at tide changes, especially near the cuts through the grass flats. If you're launching at low slack, you'll have a more relaxed paddle than if you catch a dropping tide mid-session. Windy Wednesdays and NOAA's tide chart for Port Richey give you the numbers closest to that area.