AVX2 may be faster than SSE2 though not all CPUs support it (Steam > Help > System Information > Processor Information > AVX2). Freetype uses freetype as the text rasterizer and includes some custom fonts, which results in better looking text but larger DLL sizes. PDBs are for developer use.
If nightly.link is down or can't be accessed, you can still download through GitHub with an account.
Read about Amalgam's documentation and features here.