This is like trying to find your lost ocean liner, using a magnifying glass to look at the dock.
If you're early in a project, the key to performance is simplicity, particularly of data structure design. Don't put in anything fancy or complicated before you've demonstrated a need for it.
Once you're into the project, performance problems creep in.
They're just like bugs except less obvious.
However, they are actually more easy to find than bugs.
I depend on the random-pausing method.
Maybe you will find at some point that floating-point is causing a problem, maybe not.
When you do, that is the time to worry about it, not before.