I use Regular plus a faster-acting insulin such as Novolog or Apidra. (Humalog doesn't work for me. I mean it doesn't work -- might as well be water.)
Compared to Humalog or Novolog or Apidra, Regular will differ in the following ways:
(1) It will take longer to begin working, so you will need to build in more lead time between injecting and eating. As with everything concerning diabetes, the exact effect varies from individual to individual. There are people for whom it starts working in as little as 20 minutes. For me it's nearly an hour. The average seems to be between 30 and 45 minutes.
(2) The effect will be more gradual and will last longer, usually around 4 or 5 hours. (Again, you will have to test and measure to see how it actually behaves for you specifically.) This means it will give a poorer response curve for high carb meals, and a better response curve for slower-digesting protein. I choose my insulin in part based on what the meal will consist of.
(3) For most people, Regular will be less powerful than the fast-acting analogs. Again, the difference will depend on the individual. For me, it takes 1 1/2 units of Regular to get the same effect as 1 unit of, say, Novolog.
As usual, you can only take any of these as rough guidelines. The only way to know how it will work for you is to try it and test, test, test. And log the results. That's the only way to obtain reliable data.