Trouble is with small bolts, the tools get very delicate and if you snap them, you still have your stuck bolt and now it has a really really hard to drill through tool stuck in it too. IME they are a last resort, for anything under M8. Bearing in mind that the bolt is obviously sufficiently stuck that the original head broke or rounded, which means you need the tool to be stronger than that.
Left handed drillbit, yes. Bolt specific extractor like the Irwin and Laser ones posted, oh god yes. (torx is a decent substitite for cap heads) Cut off top of bolt, remove all the other ones then molegrip it out once the tension’s off, sometimes. Cut a slot in it and screwdriver it out, sometimes. Heat, penetrating oil, almost goes without saying. If you can weld then whole new set of rules… And then after all that, extractor tool.