Just posting my experience in here with hopes that it'll help others that are upgrading/purchasing Vegas Pro/Post with the included Boris FX Transitions Unit.
I upgraded to Vegas Post 19 and was sent an email with download links for Vegas 19, Sound Forge, Boris FX Continuum Transitions Unit, and Boris FX Primatte Studio.
The Vegas 19 and Sound Forge installations went perfectly, but the Boris FX installs were confusing. It seemed like Transitions Unit and Primatte Studio were fighting each other. I think that for my install of Vegas Post, the Primatte Studio download link/installation was redundant, and created confusion for me and the software. I think it would be the same for a Vegas Pro install since Primatte Studio is included with it as well.
I wasn't fully aware of the trouble at first, which led me to clicking the respective links for Transitions Unit and Primatte Studio and trying to install each. I also didn't understand the option for leaving/removing unlicensed Boris FX software.
The problem I was having was not being able to use some of the Boris FX within Vegas. I think the cache built for leaving the unlicensed software and when one of my reinstalls removed the unlicensed software, Vegas left the options for some of the FX that weren't installed. I was met with FX not working and separate seemingly unrelated Vegas crashes.
I also wasn't fully aware of what was included with Boris FX Continuum Transitions Unit, and was trying to use FX that weren't a part of it. After a bit of research, I started to realize this and reflected on my installation process.
I looked through the forums and saw a recommendation of "clearing the cache" for a different problem someone was having.
To clear the cache: From desktop, hold Ctrl and Shift, then double click the Vegas icon. You'll be greeted with a pop up asking you if you want to reset defaults, as well as a check box for "Clearing the cache".
After doing this, I reinstalled only the Boris FX Continuum Transitions Unit.
All of the non-working FX that weren't licensed were removed, and everything worked! Naturally I was relieved, and could then see how much of an improvement it was to work with Vegas 19.