Storing STRING and BOOL in a STRING Column?
Use tinyint for these and use boolean in your ORM. SO it will automatically mapped from boolean to 0 and 1.

Its not good way to store boolean as string and then checking the value and assigning bool value on basis of string match.

For boolean just 0 and 1 value in your column as tinyint will solve your problem. For other column which arestring and if cardinality of the values in that column is very small as compared to overall data size then you can either use ENUM datatype or normalize table by joining it with another table containing those values.