You'll find out once it's assembled. If there is play and you use the 609 (personally I'd recommend using it on those two points after stripping + anodizing anyway), the key is to be generous with the stuff, assemble it quickly, and then leave it and don't touch/move it for at least 12 hours, preferably 24. If there was play and there is still play afterwards you'll need to re-do it but generally it works first go, and once it works it will stay put virtually forever.
I agree with your point on the lower BB and found the bike faster to ride when it wasn't so low which I've detailed in previous posts in this thread if you skim back over the pages. My solution was to run a -1* reducer cup only (rather than 1.5 - 2) and drop the fork in the crowns to wind the head angle out further as needed - with the added bonus of raising the BB. I run a Fox 40 so there is much more range of height adjustment than a Boxxer. For alps riding I had the bike at ~62 deg and 13.8" BB or so, for less steep stuff I lower the fork a little so it's closer to ~63 deg and 13.75" BB. The extra frontend height can be counteracted quite easy with lower bars if needed. I don't recommend an angleset as a movable interface is an added point of failure - stick with the fixed cups if you ever get them (Works Components cups are my tool of choice).
I agree with your point on the lower BB and found the bike faster to ride when it wasn't so low which I've detailed in previous posts in this thread if you skim back over the pages. My solution was to run a -1* reducer cup only (rather than 1.5 - 2) and drop the fork in the crowns to wind the head angle out further as needed - with the added bonus of raising the BB. I run a Fox 40 so there is much more range of height adjustment than a Boxxer. For alps riding I had the bike at ~62 deg and 13.8" BB or so, for less steep stuff I lower the fork a little so it's closer to ~63 deg and 13.75" BB. The extra frontend height can be counteracted quite easy with lower bars if needed. I don't recommend an angleset as a movable interface is an added point of failure - stick with the fixed cups if you ever get them (Works Components cups are my tool of choice).