Just wanted to share my experience because I went through this exact crisis last year when I upgraded. I saved up forever for the Canon RF 85mm f1.2 L USM. The image quality is honestly unreal, and it really shows off what these high-res sensors can do. But you definitely want to be careful with the weight. Holding that massive block of glass during a long shoot is no joke, and I ended up with major wrist fatigue after just two hours. Because of that, I actually started renting the Canon RF 70-200mm f2.8 L IS USM for my studio work, and it kind of changed everything. You might want to consider it as an alternative. It's surprisingly light for a zoom, and having that focal range in a tight Chicago studio is a lifesaver. The big tradeoff is losing that ultra-wide f1.2 aperture, but at f2.8, the autofocus is still lightning fast and the compression at 100mm+ is gorgeous. Also, if you do decide to look at the Canon RF 135mm f1.8 L IS USM, just make sure to measure your shooting distance first. If your studio is under 20 feet deep, you're gonna struggle to get anything wider than tight headshots. Hit me up if you want to know more about how they handle in low light, happy to share what I've learned!

Honestly, I was in the same boat and ended up going with the Canon RF 85mm f2 Macro IS STM. I have been super happy with it for my indoor shoots. There are absolutely no complaints from my clients about sharpness, and it works well with the new autofocus tracking. For a tight studio space, 85mm is definitely the sweet spot. If you went with the 135mm, you would be backing into the walls constantly. The best part is it weighs almost nothing compared to the f1.2 beast, so your wrists will actually survive a three-hour session. It is just a very safe, reliable lens that gets the job done and leaves you with plenty of extra cash.

Just saw this thread. ^ This. Also, regarding that f2 macro option mentioned earlier, unfortunately I had some real issues with it in a dimmer studio setting. The autofocus felt kinda sluggish and it just wasnt as good as expected for tracking fast movements, which seems like a waste on the new R5 II. And the f1.2 is just a brick. My wrist was killing me after an hour, definitely not worth the physical pain or the crazy price tag tbh. Honestly, instead of guessing, you should just search for this online. There are tons of side-by-side tests:

• Search YouTube for '85mm vs 135mm indoor studio space' to see the actual working distances.
• Check the Canon subreddit for threads on 'R5 II portrait setup under 2000' to see what others decided on.
• Look up rental comparison videos to see how they handle in-hand. Seriously, just spend ten minutes looking up those videos and threads. Seeing the actual physical distance in a small room will make your decision way easier than reading our random opinions.