MinMax --
How does the need for guest race goods, which have a fairly significant lead time / storage capacity in my city get handled in your KP spending decisions?
Is the assumption that portal profits will be used as needed for those if short and the tech is full of KP?
Well, the idea is to design the build in such a way that you don't get short. This is not always possible
Still, research tree up and including Woodelves is setup in such a way that you don't need settlement goods until later in the chapter, so for the most part it doesn't interfere with your lead time to production setup.
There are a few exceptions here and there - primary example would be Orcs. There is a trap there - it may seem that right after unlocking Rally Point you need settlement goods to move forward. Which is technically true
This is pretty early. But trying to get some productions from your very early settlement is shooting yourself in the foot long term there. Instead, if you take a look at City Expansion 33 tech (which needs 450 shrooms of wisdom) and is available at the same time as Rally Points, you may notice that 3 subsequent techs after that one do not require any settlement goods. This means that if you pass that gate (yep, with PPs), you unlock 57+50+60+68=235 KP sink. If you play this right, you may get up to a week extra time, during which you go bananas building and upgrading your settlement. Depending on the level of your portal, this is only 25%-75% worth of PPs. This was more than enough time for me to avoid tech lock in the Orcs completely, and even finish production couple of days early (that's with ~60KP/day intake on average)
Another case would be S&D chapter. I haven't done a full analysis yet, but it seems that this is a first chapter that is designed for tech lock (probably to force AW upgrades before Halflings). Unlike Orcs, there it's not a question of how much space you can afford to deploy (max structure is fixed). You're hard capped on the number of apprentices that is generated, and this is capped pretty low. It seems to me that unless your KP accumulation is extremely low (no tournaments / special buildings etc), you will be tech locked there for quite some time. Unless you deploy a ton of PPs - I believe we're talking 200-400% worth of PP. Which is doable, but there is really no other way around that in this case. If my preliminary calculations are correct