Some findings/guide about the "romance"/marriage system.
All 4 races except Dwarf can NTR be avoided.
Elf, Gnome, and Human have "choice based" NTR events before marriage, Sylph and Dwarf (only gets NTR when marrying) seems to not have one.
Elf is by going to the "right path" (go towards penske pass and use magic ladder, don't go towards the orchard path if you want to avoid NTR) to save her on time, Gnome needs you to do something early on (go near the gnome village before going into sapphire town and kill the bandits), Human needs you to have the mystic eye spell learned.
Dwarf is the only one that you cannot postpone marriage once you reach the marriageable status. The other 4 races have a choice that you can postpone marriage. Dwarf choice is either "fuck off let's break up" (not exact words and her romance system is dead once you choose this) or marry.
The "wife satisfaction" on dialogue when sleeping with her is based on the love status (not on the penis enlargement pills lol, but I never tested it yet). The dialogue changes to wife is satisfied only when love is at 95+ or maybe 98-100 (dialogue may vary but the tone is the same). There may be 3 different "sleeping with wife dialogue". One for High affection/love which she is satisfied with the sex, one with medium/not high enough love (This can reach up to 90-95 love. Which everytime you sleep with wife she is unsatisfied and her love meter goes down) and LOW/no love where she outright will not sleep with the MC.
The dick enlargement pills do increase the stats in the stat page of "satisfaction" but IDK if it changes the dialogue with the MC even if love is medium/low. While High love 98-100 will still give satisfaction dialogue even though the satisfaction in the stat page is 1 star over 5 lol.
A girl also cannot be abducted by Wild bull once they become wife.
You can also "increase the love" of a girl even when she is just level 1 and your party is level 50 (what I mean by this is you can easily create a bride and max romance without needing to explore shit/level up/grind once you meet the requirements of marriage. The first thing you need to do is feed her favorite food. Once she has at least 1 love you can talk to her in the inn. Spam talking to her and get her events leading up to marriage (you may need to do something specific depending on race). Even when her trust is 0 to anyone in the party, she can still be married lol
Also there are some "fake choices" that will either end the romance path or can be continued when leading up to the marriage choice. For example in the Human scenario (whether you avoid or got NTR) there is a choice where the MC can say "I will marry you" or something. It does not insta lead into marriage (there are some events left) but choosing the other option will stop the romance from progressing and they will just turn into a generic party member. The other one is for the gnome wherein the choice is "I will stay by your side or protect you forever" (something like that) but the marriage choice is still further off.
There is also a "technique" or bed skill stat that can be gained when having sex with wife that can further increase the satisfaction stat. Technique can be checked in the snow village, there is a woman npc there that can see male sex stats. Credit to
Melp
Another thing is that a girl cannot be removed from the party when they become the wife (they become essential same as MC and Max) so events that makes a party member go away temporarily will not occur with wife (Like WB abduction, enemies removing a party member for 1 fight, etc. [an exception to this may be the boss at the swamp of the dead that disappears your party member mid battle]). The recent acts stat list can be "cleared" by removing the party member and re adding them back (the foster recent acts for elf disappeared when I removed her from party and re added her).
That is my findings so far, do correct me if some information is wrong or some additions to this.