Is the general consensus that I should play the vanilla game before I play the CN mod or does that not really matter?
Right away I noticed that my MP ticks down nonstop so I'm guessing the difficulty is a lot higher in the CN mod.
Honestly, the CN mod has some nice features that make it worth using, as long as you are careful with the settings. For example being able to change your 'Lust Stage' (which gates some content) just by visiting home means you don't have to grind scenes/encounters, and there are many more things it allows you to do. That said, and speaking only for myself, the entirely
optional increased difficulty options actually make the game worse - all it does if force you to grind and spend a lot more time in dungeons than you probably want to and doesn't really add much actual value to the experience. As noted Lust generally gates what scenes you can access or can happen to you, so all extra difficulty options mean is you will spend hours and hours extra engaging with the battle content and/or trapped in the same lose scene loops over and over, which isn't what most are likely playing for.
Example? The above gym teacher content. Initially, he'll make the heroine blow him and torment her with vibrators. He won't actually fuck the heroine, which is something that storywise he has been waiting for a chance to do for years, until Lust 100+. It feels unrealistic and gamey. You have to get to 99 Lust before you can 'unlock' the next set of scenes and each encounter gives a +2 or +3, and if for arguments sake you are largely aiming to win you might be getting the occasional +1 from being passively groped or encountering traps, so you might be forced to repeat his encounters 30+ times to progress. That's more days than most playthroughs would take. Same again for a certain dungeon, where the heroine can be captured and assaulted on contact by the enemies, they will only inflict the 'first' tier of their scenes at 1-99 Lust. Tier 2 is Lust 100-200(?) and opens up most scenes while not turning the heroine into a mindbroken slut.
The most 'satisfying' way to play for me is standard or normal hard mode using CN mode and just 'start' at Lust 100. You still start out with a virgin heroine, you will still get all the first tier of scenes before the following escalations, but you don't hit a wall where you have to artificially 'grind' Lust.