Hi srw2. Congrats on your purchase. I currently have a 2018 Preferred without the Bose, but I've posted on here a few times about attempting to "wake up" the Bose sub in the rear tire well. Short story there, no luck and they say it can't be done. Anyhow....
To be honest, I'm not able to share any good info about what you asked about above, because I don't have the Bose in mine. However, I work at a Volvo and Mazda store (and have worked in the past with Bose on several GM products as well as limited on Honda). With the Mazda system, I can tell you that there are certainly different Bose "systems" depending on the exact Mazda you get. For example, the CX3 small CUV has the optional Bose in the higher trims. However, it's quite different from the Bose in the higher level (more expensive) CX5 trim. So my point is that I'm thinking the Encore may have a more basic Bose by name only. In other words, when I was doing my research, I did find out that the Encore's entire system with the Bose is nearly identical to my system except for the 4 door speakers. Yup, that's right. The two tweeters in the A-pillars? Same part numbers. The Bose sub in the tire-well? Same part numbers. Head unit? Same. In fact, the power pack (not sure what it's called, but under the rear seat) is even the same part number! That's why I was hoping the dealership could just program my system to wake up the sub in the back. Sadly, they said it can't be done. But back to the differences between the Bose and mine: The only parts with different part numbers were the four 6.5" door speakers, but I replaced mine with much better quality speakers anyhow (you can read about that in my other posts if you want).
So to bring this to a close, I think you probably have everything you are entitled to in your car. I don't think you have Centerpoint or any of those items. From what I can find, the Buick Encore only offers the Bose Premium 7 speaker system. Here is a link to the Bose site and where it really tells a lot about the different systems in different cars. https://automotive.bose.com/vehicles/buick
Anyhow, welcome and hope this helps. I'll check back in a few weeks to see if you found this helpful.