The best choice depends on the scale you want.  For very small scales, Natural Earth vector files should work well, and has three levels of detail.

You must check the scale of the vectors, and whether they work for the scale you will be using.

Many of these are huge, and could benefit from being subset before use.

Many also have multiple small line segments, and could benefit from a dissolve operation.

Most of these are lines, but in some cases for islands the lines close and you can convert them to a polygon or treat them as one.

Last revision 9/17/2021