You can find info on max and min limitations for Handy here: https://discuss.eroscripts.com/t/some-guides-and-formulas-you-can-use-when-scripting-for-the-handy-using-ofs/35396
Your second question, what feels good, is super subjective. I’m actually a bit surprised by how big the difference seem to be in what people enjoy. I like the slowest scripts around, can’t last more than a couple of minutes with a script above 200 average speed. But many users really seem to like the super intense kind.