I honestly don't know much about OD1 steerers on other Giant road bikes. I did crack the front forks on my 2020 Propel Advanced Pro and had to find a replacement set. In searching, I never saw a set of forks with an OD1 steerer on a pre 2018 Propel with in anything but aluminum. <shrug> Yeah, OD2 is kind of a pain, but only if you're looking to switch out components. I actually really like the look and the internal routing system on the 2018+ Propel, the bearings only have to operate through like 45 degrees from center at the most, so I don't feel the need to modify the stock set up. The frame came with every thing I needed and more. I absolutely hate the external routing on the TCR. It's a great frame, but until they clean up the looks...
Anyway, yeah, be careful with too many spacers on the 099.