As of this build, the four routes are pretty binary, there's two choices that it branches at and those are the only thing that decide the route you get, other options only change the next few messages as far as I can tell. Gifts might change this later, they were removed from this latest version, probably because giving even 1 gift changed the route.
The routes are based on:
A) Did you have 2 or 1 love at the end, aka did you get the -1 Love from not replying the first time (game gives you two chances, you have to ignore both and not reply)
B) Did you have 5 or 4 purity, aka did you get a -1 Purity. This used to be from letting her drink or not, now it seems to be entirely based on if you bring up the bowser wanting sex option in the "Why's are we getting along" -> He's just lonely vs He wants sex reply, question is slightly rephrased based on A, if you don't reply the game/Peach assumes Lonely.
They're labeled as this right now:
2 Love 5 Purity = Naive Girlfriend
1 Love 5 Purity = Naive Ex-Girlfriend
2 Love 4 Purity = Ruined Princess
1 Love 4 Purity = Evil Ex-Girlfriend
After the kidnapping, the only things that are changed from the previous version are one scene now being animated, the 2 new sex animations which are pretty simple loops, and some of the later animations having some variants they randomly swap between when I believe they were just loops before. The routes from there are unchanged, like before having 4 or less Purity (from either the above option in B or saying you did look at the pictures) causes a different version of the bj section than 5 Purity, which is the only major branching path post kidnapping, everything sex onwards is identical no matter what except for the final message that changes if you manage to still have high Love at the very end.
Looking forward to seeing where things develop from here!