WGS84 datum are usually given as coordinates in a fully decimal notation, usually with 5 decimal places, so for latitude (-90 to +90) you could use decimal(7, 5) (-90.00000 to 90.00000), for longitude you could use decimal(8, 5) (-180.00000 to 180.00000).
.00001 gives an precision of around a meter at the equator
The DECIMAL/NUMERIC data type is a fixed precision scaled integer and both positive and negative parts of the range are always available – they do not affect the precision or scale (there is obviously storage required for it, but you don’t get a choice about that for DECIMAL)