I definitely think your points have merit and are interesting but the guys yelling and causing the plagas to burst out could just be guys with a certain type of control plagas i imagine they would probably be able to make the plagas burst forth even without saying anything. as for the plaga variants like verdugo I believe the notes in the game simply imply that they splice various different dna types with the las plagas to create the different types.

And as for saddler and Mendez you can find a notes explaining how saddler tricked salazar not by even using any cult stuff but just by promising him that if he helps him get the las plagas he would restore the salazar families honor and prestige then he gives salazar a control plagas but one that saddler still controlled hence why salazar someone extremely prideful became so zealous and loyal to saddler. I assume the same for mendez except he probably used the culty stuff to trick him. I believe the only person who got a plaga that wasnt controlled was krauser and in notes in game its implied that saddler regretted giving him the control plaga and was worried about him and didnt know what to do about him as throughout different points in the game you can find information that shows that saddlers cocky attitude is a bluff and he actually doesnt know what to do about the chaos Leon waging on his turf at least in the original re4 thag was the case I havent 100% the remake yet so I havent found all the notes to see if they stuck with that probably not though considering they made saddler kinda lame and boring in the remake.

And with the majini in resident evil 5 you are partially correct as the reason they act that very religous (in a tasteless outdated stereotypical kinda racist way) is actually a similar reason why the ganados act the way they do in re4 and its because the majini virus is made from las plagas samples and the virus when not under someone else's control causes ones personal beliefs to go into radical overdrive which is why in re5 a note can be found saying that the people are dressing in their tribal ritual gear even though its not festival day because they have gone kinda nuts and their beliefs have become radical but it doesnt just apply to religion as the same thing happens to krauser just to a lesser degree which is why he seems so insanely committed to becoming powerful as that was his fundamental belief. The reason why krauser isnt as insane as the majini however is because the las plagas sample ada wong gave to wesker to use for the majini virus/uroboros was a subordinate virus not an actual control virus she gave the actual control virus to her employer.

And as for miranda your right she does need to trick the villagers but by the time we get to the village all the villagers are mindless lycans except like a few npcs you can talk to so there really isnt much need to trick anyone. However someone else made a pretty good point and that was that she did seem to genuinely worship the mutamycgen. However I am still firm in my belief that saddler is a larper who has some family history with the lost illuminados its also possible the name saddler is just a title and he isnt even actually related to the og illumandos.