No worries. I did a test run with the Darker Shadowlands mod to see what you'd be up against.
My suggestion would be to make an immediate B-line for the Gauntlet of Shar and camp there, because the standard camp above ground is probably going to give you nightmares. It's pretty well lit. If you squint and turn off all the torches or just book it straight for the bedroll without looking around too much maybe, but I don't know. I think camping in the Gauntlet of Shar camp is your better bet, just gotta get there.
Out on the road I'd have everyone douse their torches and just run I think. Then get the blessings ASAP, so you won't take damage from the Shadowcurse for not having a light source up. Moonrise is also pretty dark, so if you keep your head down and stick to the main rooms maybe, but there's a lot of vines up top. Maybe there's a mod that turns off all the torches too, or dials back the glow effects on some of the environmental stuff?
I'm not sure its a great solution, because there will probably be instances where something looks even more pronounced or highlighted because of how things are lit in high contrast. You know like one second everything will be mostly black and in shadow, but then you round a corner and maybe catch something unavoidable on a wall or lit by an environmental torch or whatever. The Act II to III transition isn't really like the Act I to II transition, there's no way to blow past the Shadowfell or the big fight at the end of Act II. It's much more of a funnel here and gotta hit the main beats to advance the story, but I think you could probably avoid most of the side stuff. You'd be down some cash and underlevelled probably doing that, but could maybe make it up on the back end in Act III?
Anyhow, it's tough, since you wouldn't really no what to avoid till you get there. The main offender is probably the standard camp for Act II though, especially by Withers and along the cliff rocks. I think you'd just want to avoid it altogether.
The villainous path might be more straightforward since that get's you a bit closer to Moonrise Towers initially and you don't really have to fret off the lifting the Shadowcurse as much in that case. Going into much more is spoilerville, but trying to avoid the whole Shadowlands is very tricky. Like probably your optimal solution would be some sort of blur, or maybe moss or poison leaves or whatever to just cover over those visuals on those trees, but it's probably a lot of work. For Karniss I'd maybe use one of those mods that turns all the spiders into Sheep, or just try to avoid his cutscene so you don't have to watch his close up. Otherwise, if you can just get to the Last Light, Moonrise and the Gauntlet you can sorta portal back and forth. The House in Deep shadow will be harder to get to, but again maybe with a squint and dash. I would not linger in these lands over long though.
You requested no screens, so I won't go there. To preview what it looks with the Darker lighting mod I have a few screens on the last page of this thread at the tavern... The more recent posts will have spoilers for you though, since you haven't gotten there yet (also Dark Urge), but post 111 shows the above ground camp in Act II and one of the battles areas where the trees are very prominent, in case peeps are curious what visual elements are being referred to.
https://tavernrpg.com/threads/bg3-honour-mode-strategy-tactics-many-spoilers.388/page-6#post-11998
