struct will have fixed memory size.

When transpiled to JS, a struct is just an object of data. So it will have smaller memory footprint.

while objects need to have each method defined individually.

I won't do that. I will do the same as for enums: static dispatch.

enum Weekday {
    MONDAY
    TUESDAY
    WEDNESDAY
    THURSDAY
    FRIDAY
    SATURDAY
    SUNDAY

    isWeekend(): Boolean => this == SATURDAY | SUNDAY
}
func foobar(day: Weekday) {
    if day.isWeekend() {
    }
}

is transpiled as (I've removed the dispatch code when the types aren't know)

const Weekday = Helper.enum(Number, {
    MONDAY: 0,
    TUESDAY: 1,
    WEDNESDAY: 2,
    THURSDAY: 3,
    FRIDAY: 4,
    SATURDAY: 5,
    SUNDAY: 6
});
Weekday.__ks_func_isWeekend_0 = function(that) {
    return that === Weekday.SATURDAY || that === Weekday.SUNDAY;
};
function foobar(day) {
    if(Weekday.__ks_func_isWeekend_0(day)) {
    }
}

Kaoscript won't be limited to JS, it will be transpiled to other languages like Lua, Zig or Rust.

I went through the source code, I also interested in building transpilers. So it would be kind of u to suggest the resources that aided in building this project: like books, repos etc..

I'm planning a rewrite the current transpiler since the semantic analysis is limited and the code generation isn't separated with the other steps. (I already have a prototype)
So far no book, I've used articles found on internet and looked at Typescript, Nim, Zig, Babel and others compilers.