Generally speaking, items you can uncheck in the startup menu are not necessary for the computer to run per se. Though some of these may be stuff you rely on while using your computer. For instance, on my system, I uncheck everything except for my graphics and audio drivers
and my firewall. If you're asking about the list of programs in your startup menu, that depends on what you have installed on your computer.
When you run your system in safe mode, that basically means that it doesn't run anything from the startup menu, and disables almost all of the services as well, and safe mode is usually the most reliable startup. You shouldn't worry about unchecking anything - worst case scenario, you go back and check them again.
If you want help on deciding what's good or not good to uncheck, you can post a list or screen shot of your startup menu items, and I will be glad to help you decide. Also, a quick Google search of each item can tell you precisely what each item is.