Soho is a wonderful place for a lot of things you've mentioned! You could spend weeks i just that area honestly... To start you off, you might want to check out what's on at the Photographer's gallery when you're in town. They have some great exhibitions sometimes!
Hard not to recommend the natural history, science, and V&A museums, which are all in Kensington and easy to get to from Soho. They are all free entry and often have great free exhibitions alongside some paid optional wings. You can take a walk through Hyde Park while you're there, too! Personally, though, nothing beats the Tate Modern which is also super easy to get to from Soho, and again has free entry to almost all of it.
Soho obviously has a big reputation for queer history in London — there's plenty of hotspots and bars worth looking into in the area.
Thrifting, you might have more luck in north and east london. If you just want the highlights, it's hard to go wrong shopping and a bagel in Brick Lane.
Bonus — Flat White in Soho has my favourite coffee in London :)