@The family raft slide with the 2-3 fountains, that raft definitely felt snugger (and I am medium slimish) mainly because the raft was firmer ie no give / no sinking in.
The Taniwawa (?) tubes are front facing dinghies for 1-2 people, so more likely to be able to ride as can go as a 1. There are four of those to enjoy on one tower. Similarly Punga Racers is a solo ride and also four of those.
Appreciate you want to go on family raft rides - so FYI each tower contains two family raft rides and both rides load on the same open platform, so worse case, if you can’t go on (higher wall) blue turtle you should be able to transfer / walk across to the green family raft ride.
Good luck.