This statement
I understand what you said, but that doesn't take away the impression that he was just lucky and didn't plan anything
Do you really understand? Because the wiretap scene should've removed that impression entirely. In these narratives that use an unreliable narrator, readers' impressions will vary BUT only during the first read through. Once new and reliable info is revealed, most readers will reevaluate their perspective of the situation and use it as a tool to ascertain the credibility of the preceding narration. In our case, this new and reliable information is the wiretap scene. The wiretap scene is neither a dream nor a delusion and this establishes the fact that MC managed to inject the wiretap to either Teresa or Victoria.
With this in mind, we should reinterpret the previous actions of the MC regarding this case. I replayed the "Who did it" part of the case and below are the events that follow:
1) MC goes to the office to check the forensic report. He feels he is being followed but notes it as just his imagination.
2) Spade tells that the report is late and says that when this happens, someone is withholding the information. He then tells MC to visit Moe.
3) Mall visit. MC takes wiretap and cams. Moe tells that this church is shady as shit and its Mother Superior, usually a well-known individual, doesn't even have a single info or pic in the church's own database. MC has an idea and goes home
4) MC proceeds with his cam idea to bait the nuns into making a move. Goes home after installing.
5) Start of train scene. MC is standing in train, receives message from Moe which visibly surprises him. Then he feels he is being followed again but this time notes "What a fascinating situation". MC then decides to take a seat.
6) Train encounter. MC ponders about the case then, due to frustration, exclaims aloud "Damn you Mother Superior" coincidentally startling a beautiful lady. She asks if MC is okay then MC casually reveals he's a detective and there's a case in a nearby church. Turns out the lady goes to the church and she asks MC who he suspects but instead of taking caution, MC didn't give two shits and said he is interested with the Mother Superior; an ugly and old hag who can't possibly be sane after all the years of no sex. Then the lady says the Mother Superior will be hard to interrogate. MC said that detectives have their ways and he will be 10 steps ahead and his actions will be designed to bend the Mother Superior and make her spill the truth. Train ride ends.
7) In front of church. Lady introduces herself as Victoria and tells MC she will have his babies if he solves the case but sadly, looks like MC has no leads. MC points out the wall camera and calls it his lead. He even gives out his 3 step plan vs the Mother Superior; Identify the opponent, gather info then set the trap. Even bragged that "Being a detective is like chess. Disguise your moves and lure the opponent to a false sense of security". Then Victoria hugged MC, he thought "wow she hugged me.. this is perfect" then Victoria calls MC naughty for caressing her neck and that it's all tingly now. He apologized then they went to the church.
8) Church. MC got bitchslapped. Victoria revealed as the Mother Superior. Then MC, in apparent anger, pathetically and desperately accuses Victoria then demanded the key to the library. Victoria obliges, shows the key in a safe, states that she's the only one that know the combination and that she's not in the church when the incident happened. MC left after.
As written above, these are the events that should be reevaluated after the wiretap scene. Based on the info "MC managed to inject the wiretap", it can be safely said that the MC succeeded. But is it because the MC just got lucky? No, of course not. The MC already formulated a plan to bait the nuns the moment he saw Moe's 2 cams.
Whether or not he received Moe's message and; Whether or not he met the Mother Superior in the train, it doesn't change the fact that the MC already has a plan even before going to install the cams. MC wasn't just lucky, he actually has a plan.
Now if this is about the statement
I understand what you said, I just think it could have been more consistent, instead of making his thoughts contradict his actions
Again. It has been hinted multiple times that MC may be suffering from some sort of dissociation, making him an unreliable narrator. His thoughts are neither 100% truth nor 100% complete, but that doesn't mean they are not important. It is up to the readers to determine the credibility of the narration but that's what the wiretap scene is for. It sets an irrefutable fact and helps the reader work out the story with this fact as a guide.
So during the train scene, MC kept thinking about how beautiful she is and all 15 steps of kama sutra even when Victoria revealed suspicious info about herself. Why? Because he want to come off as an easygoing and incompetent detective, his thoughts are for himself to keep staying in character. He already knows he is dealing with the Mother Superior so why bother think about these
"how does she know so much about the superior mother?" or when she mentions the time she didn't go to church, "so she didn't go to church for 2 weeks... about as long as the superior mother retires... interesting"
What's my basis on this? Because when Moe messaged him, he reacted in visible surprise then he turned around to look at the unusual feeling and noted it as "What a fascinating situation". Remember that in both times, Victoria was caught in the peripheral vision of the MC. He knows he is being followed by this girl, add to it Moe's message and his reaction to this situation then it isn't unreasonable to assume that the message MC received is a pic of the Mother Superior.
Then here's another statement of yours
If he's planning something, at least make it look like he's planning it
This one is understandable if it's your first read through. But after the, you-guessed-it, wiretap scene then this is just sad. As shown in the event sequence above, take note of all the bolded phrases on the list then use the "MC managed to inject the wiretap" fact to interpret it. Was it just coincidence that he startled Victoria? Why did MC casually insult the Mother Superior infront of Victoria even though he knows she's a regular churchgoer? Was it just carelessness that made the MC ignore all the signs that Victoria might be the Mother Superior? Why would MC point out the cam to Victoria instead of the nuns? This shit reeks of premeditation. The moment he received the message from Moe, he adapted his plan to include the Mother Superior. He made contact with her, portrayed incompetence, provoked her, used the cam bait on her instead of the nuns, injected the wiretap and even managed to confirm the location of the library key. With so many obvious hints that's revealed after the wiretap scene, it's just sad if these results are still attributed to luck instead of planning.
I say you follow dev's advice and reread. And I won't deny MC is lucky. He banged 2 Vanderbilts already after all. But in this Victoria case, its not luck at play.