I had much hope for project references with --incremental and --watch mode to be quicker than using external tools, but they still seem to recompile a lot (and so take a long time). Or maybe just because I am some tsc versions behind?
I had the same experience on Typescript 3.4.5. I hear that project references with incremental/watch are more performant on newer versions. (Notion is stuck on 3.4 because of this issue: https://github.com/microsoft/TypeScript/issues/31445)