unfortunately, there's nothing like experience, and that costs money. If you shoot the mid range a lot, you'll want to shoot both f4 and f2.8 variants eventually. I've gone back and forth on the f4 and f2.8 and historically, I favor f2.8. Just recently, I've gotten the urge for 2.8 again for event shooting, in particular, low light video. Maybe my views are slightly distorted, I was shooting videos of a christmas carol with the 135L + 4K. Few days later, shot a christmas play with the 24-105 + 1080p.... the difference in video quality is night and day..... however, I'm not sure if it's the newer camera, bright lens, or 4K making it so much better. The difference is huge.
Sony A7siii/A7iv/ZV-1 - FE 24/1.4 - SY 24/2.8 - FE 35/2.8 - FE 50/1.8 - FE 85/1.8 - F 600/5.6 - CZ 100-300 - Tamron 17-28/2.8 - 28-75/2.8 - 28-200 RXD
Panasonic GH6 - Laowa 7.5/2 - PL 15/1.7 - P 42.5/1.8 - OM 75/1.8 - PL 10-25/1.7 - P 12-32 - P 14-140