I’m a brand new investor. So far I have a small amount of money in the SWPPX fund but I am also learning that ETFs also have their own benefits and drawbacks, so I wondering is it beneficial to have one of both types of funds or just have one type?
Investing in an ETF and a mutual fund does not offer any diversification benefit in itself. They both work the same in principal - they consist of a multitude of stocks (sometimes bonds and derivatives, depending on the type) to reduce overall risk. The differences to you are purely mechanical - ETFs trade during the day, generally have lower fees (but mostly because they are usually passive ETFs that track an index, and generally have lower initial investment requirements.
So if you had an ETF and a mutual fund that consisted of exactly the same stocks, there would be no difference to you from a risk or return standpoint. You can invest in one or the other or both. The main goal to mix different styles and strategies to gain the benefits of diversification.