I don’t know if it’s the best option, but I like using Shotcut for splitting videos; it requires understanding the basic concepts of the timeline (which is pretty easy), and exporting (which is not so straightforward).
If you can get yourself relatively competent adding and splitting clips on the timeline,
https://shotcut.org/tutorials/
post the specs of your source files and what you want to do with them and people will help you with export settings.