You are confusing two things. Usually you represent decimal numbers as rational fractions p/q with two integers. If you fix q, you get a fixed point format, if you allow q to vary, you get a floating point format. Unless you are representing rational numbers you usually limit the possible values of q, usually either powers of two or ten. Powers of two will give you your familiar floating point numbers but there are also base ten floating point numbers, for example currency data types.

BCD is a completely different thing, instead of tightly encoding an integer you encode it digit by digit wasting some fraction of a bit each time but make conversion to and from decimal numbers much easier. But there is no advantage compared to a base ten fixed or floating point representation when it comes to representable numbers.