So for the first part, as an NTR fan, I MUCH prefer avoidable NTR than not, because you have agency, and much like you said, overcoming pitfalls raises the stakes and makes attaining the love interest more meaningful.
To the second part, I also prefer the antagonists in NTR games to not be evil.
My two favorite NTR games are probably
Scars of Summer and
Hero Roy's Wedding and I'm gonna talk about both.
In Scars of Summer, the protagonist is defending his love interest against 6 antagonists. I use "defend" lightly because the NTR is very avoidable, but I also understand why they did it that way. You actively have to start the routes with each antagonist; literally doing nothing lets you avoid all NTR, though once a route is started you DO have to actively take measures to prevent the LI from being stolen by that antagonist. The game has a NG+ mechanic, so they took the "Active start" approach to let the player choose which and how many antagonists to fend off. Not all of the antagonists are evil, in fact one of them is genuinely a nice guy that loves the LI and simply puts in more effort than the MC.
Hero Roy's Wedding flips the script somewhat. Here, the MC has 4 LIs and basically the whole town is trying to steal all of them. You prevent this by picking who to spend time with and when, interrupting specific encounters, etc. The game could certainly use more polish, but the basic concept is sound. It's very easy to focus on one LI (and forsaking the other 3) and win her by the end of the game. It's also possible for a harem with more than one, even all 4, but the highest reward also comes with the highest risk, and trying to keep all four (unless you play perfectly) will probably lead to losing all four.
Honorable mention goes to
Remote Island Survivors which has a decent plot and concept, but they kinda went lazy on the gameplay loop and all the art/scenes are recycled to hell and back.
A pair that are still in development but showing a lot of promise (especially the latter) are
God's Blessing on this Cursed Ring! (an NTR Konosuba parody) and
Netoria Tactics: Revolution.