I have now started a new save game and the mc and rick could now start a relationship with kate.
Does it matter what I choose here for a future 3some? If I understand the wt correctly I can no longer deflower her if she gets with Rick before me. Correct?
Well by pulling some strings and being careful you can deflower her and get her pregnant even before rick has sex with her as her boyfriend.
I did this but of course I used cheats (could be done without it but might take more caution). First encourage Rick to start relationship with her. Let him build Affection till 5 thus triggering the relationship dialogue. Now here comes the crucial part. Not sure if this is a bug or not. But as long as you aren't present on site at 9am (when they meet to talk) he doesn't have sex with her. Meaning as long as you skip time any where in which you can't see Rick entering the inn they don't have sex. He enters at 9 every alternate day to have sex with her. I personally skipped time from home skipping directly to noon before they could meet at 9.
Also don't try to use the relationship values (cheat book) unless you know the exact values to trigger events. If you miss the game breaks and corrects itself by overruling any of your hard work. Additionally you can get her pregnant and don't tell rick about stealing her if Kate has belly grown they will act like it was their kid. I didn't follow through so not sure what happens ahead.