These are possible but not practical. This is especially true in North America, since our houses are built 99% from wooden or galvanized steel studs. This means that while the bracket may be strong enough, the wall generally is not.
Many of our customers have done so-called "semi-floating" benches or tables. Here, you use the bracket and therefore just need a small support in the middle of the project, or two supports spread out evenly in order to disperse the forces that are exercised on the project in question.
Now, if you have a steel / concrete wall and you can install massive lag bolts, expansion bolts with Hilti technology, and Hilti epoxies, it is possible to achieve this using the steel bracket without support legs.
That said, each and every application needs to get approval from structural engineers and will always be one of a kind custom-made solutions. The same applies for floating vanities. Before you attempt anything in this solution, please call and ask our advice. Note that each of these can only be achieved with the steel bracket even if no supports are wanted.
If you do have supports, the aluminum bracket can work given certain rules. Please reach out to us with any questions regarding this.