You asked

Best small prime for street photography?

For street, I'd start with a pancake lens on a small body you can carry all day. The Street guide says small and quiet beats megapixels, and zone focusing is what makes a fixed-focus setup work.

Two lenses I'd look at, both for full frame cameras:

If you're not shooting full frame, the guide also covers Micro Four Thirds bodies, which take small primes and give extra depth of field for zone focusing. If you want a camera and lens in one package, the Fujifilm X half is a small compact worth a look.

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