Opening a first brokerage account with $10k. Should I go with SWPPX, SCHX, SPLG, or VOO? And why?

Long time Reddit lurker, first time poster. I’m 46. I have a Roth IRA with Schwab using the Intelligent Portfolio. I’d like to peal off some funds from a high yield savings and get more out of the market. This will mostly be a fire and forget investment, at least until I’m done with school in a few years. I still don’t really understand the difference between a mutual fund and ETF, so if some time can be spared for the “why”, I would appreciate it.