Just wondering, will all aquatic plants survive if keep them afloat? I mean if I do not plant them in aquarium soil and just keep them afloat (considering there is adequate light and nutrients), will they survive? Sorry, I know it is a noob question.
Not all will be fine. Many need to be anchored to wood (anubias, Javas) or buried in the substrate (swords) to receive proper aeration, flow, lighting, and nutrients.
Good floaters are duckweed, water lettuce, and hornwort (which can also be planted).
Some need to feed from the substrate.
Vallisneria, Amazon sword, and Crytptocorne are among those.
Those plants that feed from the water column can be used.
Other examples beside what are already listed, are water sprite, and Hydrilla
Hydrilla above, water sprite below, both can be rooted or floated
Java fern above, Anubias below
Anubus will even send flowers above the water line
Among root feeding plants, Bacopa spp. would also grow well as floaters, particularly if it is a relatively low-energy tank, such that they don't get tossed around too much. They are faculative root feeders or at least their roots can attain nutrition when floating. Typically, when grown rooted, plants grow almost exclusively leaves along stems; when grown as floaters, they put leaves and (small) roots att along the stems.
They are a good option as they bare common at stores and easy to grow. Because of the different shape of their leaves, they provide some variation to other commonly used floaters.
I agree about duckweed being a mess. That’s why I use giant duckweed. It is significantly larger and not as sticky or unsightly once covering the tank.
Duckweed is a pain. It blooms like crazy, and you won't stop it. Red root floaters are better, and susswasertang is a submerged plant that doesn't need roots that has been forgotten. Also, Marimo Moss Balls are one.