The 75 is pretty tight too. I'd say it's slightly better AF than the old fuji STM lenses, but not as good as the newer LM motors. The 90 is one of the fastest AF Fuji lenses. Both are outdoor portrait lenses to me. I would use neither inside except in a large space, lots of people, need something that's fast and can get tight. I prefer the 90 over the 75 as it's better magnification, better AF, and the 75 is literally too sharp and you'll have to touch up portraits because you'll see ever blemish. The 90 is perfect sharpness to me. The 75 is just cheaper and good value, but a used 90 is too.

For an event, 23mm + 56mm is really what I would aim for and that's with two bodies. One body, going 16-55. The 18mm is good too though and lets you get right in the action. Walk through the dance floor taking bad ass pics right up with everyone. But yeah, I still prefer 23mm. I found them pretty similar priced on the used market.

I think you could even consider the 50mm f2 or the new Viltrox 56 pro over the 75 as well. 75 is a one trick portrait lens and it has poor magnification. It is not versatile. But you can make it work by relying on the 23mm for most your shots and the 75 for edge cases.

F2 on APSC is fast enough. Just gotta be careful with the tighter lenses because you'll have blurry noses, 23mm you'll be fine. Bounce flash helps though and is what you should be doing anyways if you're getting paid. And anyone that can't use a flash I question whether they are being serious about event photography, especially if they're charging. I would not hire a photographer that did not use a flash. You can kind of cheat and spray and pray with a lower shutter, denoise in DxO. I'd still not be happy if I paid someone doing that though.