Damn you got me curious. Always wanted a feel for DXM. But whenever I had some spare time I took a classical psychedelic like acid or mushrooms. So at this point someone 18 will handle it easier than someone 42 years older. Probably not good for blood pressure.
You are young, make sure you get some mushroom trips in!
Apparently it's a lot like ketamine. I've only used DXM, and only about 7 times between 2012-2013. It's pretty cool a few times, but then it's like... yeah, this isn't that great, especially compared to any tryptamine psychedelic. Pairs incredibly well with weed especially if your stomach gets upset, it like instantly washes it away. Extraction method is recommended either way especially given most bottles of DXM have tylenol or guaifenesin in them (the latter can cause serious vomiting and shit). I know people that took this one and were fine though. When I'd taken it, it was just a bottle of pure DXM. You basically never find these anymore unless you buy robotabs off Amazon or something. The "safest" DXM bottle I've found has doxylamine succinate in it which is basically like diphenhydramine. So you would end up having a very strange trip (or completely pass out).
I think it's cool to try out at least once, but yeah you'd probably want to do extraction, especially at your age your stomach may not handle the syrup as well as an 18 year old. I was 18 when I first tried it, going on 19. How this kid did 600mg and was even functioning is beyond me. I'd hit 400mg or so and be so outrageously gone, unable to walk straight, music sounded slowed down (but also very much more alive). My skin felt like wax and I just felt like I was in this weird dissociated dream, it was hit or miss how I'd feel. But I feel weed is crucial with it, it really enhances the good effects and reduce the negative ones. One bottle tends to have at least 400mg in it. I knew people who'd down 3 or 4, they were nuts. The more you take the higher the "plateau" you reach is or something.
Based on this, OP was potentially on a low 4th plateau, I only ever reached 3rd. The brain fog/hangover feeling the next day was what I really disliked, but damn the dreams were insanely vivid. I guess I pulled all nighters on most of them though so that didn't help.