strformat is using compile-time macro. For runtime have a look at formatFloat and formatBiggestFloat in [strutils](https://nim-lang.org/docs/strutils.html#formatBiggestFloat,BiggestFloat,FloatFormatMode,range%5B%5D,Char)
General tips: you can use [theindex](https://nim-lang.org/docs/theindex.html) if you are tracking down proc from the standard library.
