You need to go to your local bike shop and actually try riding different size frames for the bike that you want.
When I bought my most recent road bike, a Trek Emonda, I brought my old bike with me to the bike shop and told the staff to match the fit. The mechanic told me that the 2020 model had Trek's H2 fit and would require a smaller frame size to match my old bike. The 2021 model had Trek's H1.5 fit and could match my old bike with the frame size recommended by the standard size guide. The problem was the minimum stack height of the handlebars, which was too high for the 2020 model. If I had bought the 2020 model, I would have needed to get a smaller frame and swap the stem for a longer one to achieve the desired reach dimension.
I've been playing these games with my Specialized Shiv triathlon bike. I bought the frame that was recommended by the standard size guide, but I had to switch to a longer stem, which required replacing the brake and shift cables with longer ones. I also switched to shorter crank arms, which required changing the bottom bracket and chainrings.