New to loom beading have questions

So I got this cheap kit and have questions. 1 - i thought the string/thread was suppose to be more solid like sewing thread and not so stretchy is this true or not? And 2 - is there a way to find out the size of the beads so I can get more the same size?

So I got this cheap kit and have questions. 1 - i thought the string/thread was suppose to be more solid like sewing thread and not so stretchy is this true or not? And 2 - is there a way to find out the size of the beads so I can get more the same size?