There seem to be a lot of confusion in your post.
x = @(t) [something]
is a single function, regardless of the something. In your example something is a 3x1 matrix but it's irrelevant. There is only one function whose handle is stored in x.
Can I change the format of the output function
Functions do not have format. If your function uses the value -6.431041321077914e-1 with that many decimals, it's because you have written that many decimals. If you want less significant digits, write less digits. If somehow that function code was automatically generated by str2func for exmaple, then you need to change the code that put that numeric value into string, either sprintf or num2str or similar, to print the number with the required precision. format only affects the way numbers are displayed on the command line, never what is coded.
can I reshape this function to be an array of 3 functions
Again, there is only one function, which returns a 3x1 array. An array of function would be
x = {@(t) exp(t.*(-6.431041321077914e-1));
@(t) exp(t.*(12.4342817231314e-1));
@(t) exp(t.*(-6.431041321077914e-1)).*4.35559619931756e-1-exp(t.*(-3.07978528369903e-1)}
which is a completely different beast from what you have. In particular, you would not be able to just write x(somevalue) to evaluate all 3 functions at once.
The main point here is ...
I'm afraid I understand your main point or rather I don't understand what problem you are having. I suspect you need to backtrack a little and explain how you arrived at the point where you are now.
