One floating license is needed for each concurrent user. For example, with one floating license, any number of users can have the software installed, but only one can use it at at a time - the others must wait for them to finish using it.
With two floating licenses, again, any number of users can have the software installed, but only two can use it at the same time - the others must wait.
Yes, you can. There are no restrictions on machines or locations.
For floating license, you can have up to concurrent use of TestWise you purchased; For named license, the registered user can use the software on different machines.