Been thinking about your question for a few hours now. Honestly, I tried using the Canon RF 16mm f/2.8 STM for a while, but it was kinda disappointing for street work. The corners were super soft and the distortion was just way worse than I expected for a dedicated prime. If you really want that classic street look, you might be better off saving up for the Sigma 18-50mm f/2.8 DC DN Contemporary instead. It is pricier, but way sharper than the cheap primes. Before you drop any cash tho, do you prefer getting really close to people for those candid shots, or are you the type who likes to stand back a bit and observe? That honestly changes everything for which lens will actually work for your style.

Congrats on the R10! Honestly, it is a fantastic little camera and you are gonna have a blast in Chicago. Dont let the crop sensor stuff stress you out, just think of it as getting a little extra reach for free. Since you want something compact for street stuff without breaking the bank, I have a couple of suggestions that have treated me well.

• The Canon RF 28mm f/2.8 STM is probably my top pick for you. It is super thin and makes the R10 feel almost like a point and shoot. It is not quite as wide as a traditional street lens on a full frame, but it works well for framing scenes without getting too close to people. No complaints on sharpness either.
• If you prefer something a bit more versatile and even cheaper, look at the Canon RF 50mm f/1.8 STM. It is basically the classic starter lens. It is really fast in low light which is great for moody evening shots downtown. It feels a bit tighter on your sensor, so you might have to step back more, but the background blur is super nice. I personally love the 28mm for the streets because it is so discreet. Just grab one, stick it on your body, and get out there! You really cant go wrong with either of these, honestly.

🙌