Yeah I was relieved to hear you could skip levels you got stuck on, but even then, I wouldn't be having much fun if I spent the whole time failing and skipping, failing and skipping.

I'm not the most capable gamer due to mild motor control impairment. I can still play most games just fine, but my fingers aren't fast or accurate enough for me to ever be an expert gamer, and I get pissed off easily when I fail at stuff.

About the hardest games I've ever beaten were Monster Hunter 3 and RE4 on Professional.

It's hard to compare it. RE4 on professional is probably harder overall (assuming you're not carrying over a save file with weapons and such), but a lot of the challenge in that game can be mitigated by good planning and resource management, where here the challenge is mostly about reflexes.

The best comparison I could think of is that the jump in difficulty from the main campaign is similar to the jump between Mario Galaxy 1 and 2. It's notably harder, but still not crazy hard.

Alrighty, good to know. It's mostly the reflex/dexterity stuff that bothers me. I had no real issues with the campaign of either Splatoon 1 or 2, but the final "world" of 2 was around where I started to near the edge of my comfort zone.

I actually did the Octo expansion but not the main campaign yet.

There's a lot of options on which levels you do, and as another poster mentioned you choose the weapons you want, and that serves as a sort of difficulty option. There were a couple of levels that I found incredibly difficult, but you can work around them. The only non-optional part that's hard is the final boss, but that's actually more of an issue with my navigational skills than anything. 

I don't know you well enough to judge, but I'm thinking it'll probably be okay. 

Okay, between being able to skip levels, and the weapons representing a difficulty setting of sorts, (I'm always gonna pick the easiest one haha) I am leaning towards giving this a go next time there's a gap in the release schedule. I did thoroughly enjoy the main campaign after all. (Which I heartily recommend)

When you say navigational skills, is it like set in a labyrinthine environment or something?