Back when MHW first released on PC there was a huge issue with the elemental hit effects when you hit a monster, lightning damage being the worst offender. Currently it seems people are having huge issue in the areas with snow on the floor that leaves tracks when you move through it, so maybe it's just something they didn't anticipate and is something they can patch up. AFAIK everyone still suffers if they have the volumetric fog option enabled, so try turning that off anyways.
Thus far I feel Iceborne is a huge improvement over World, especially in terms of the user interface. The only two issues I have with it at the moment are how unresponsive it feels when you open a new menu (you can't use the menu until it fades in 100%) and how 'cancel' is selected by default when trying to take all rewards or all harvest box items. Pretty much everything else is a huge step forwards. You can push a button to unslot every decoration now, the way layered armor works is better and you can set it to your gear sets too. You can use keyboard shortcuts while using a controller so you can have your gestures and such set to your number keys while your useful stuff is in the radial menu. There's likely more stuff but I can't think of them off the top of my head.
It is taking me quite a while to get used to the clutch claw as a lancer. It doesn't appear you can use the clutch counter reactively like you can the regular counter and every time I do the monster ends up missing me despite aiming for me so I'm sitting there exposed like a dumbass. Not only that it's pretty awkward to have to switch to grapple mode whenever a monster gets staggered so more times than I can count I've wanted to clutch onto a staggered monster only to go into a clutch counter instead.
As for the new monsters themselves I've only fought Antekadrome and skinny ice shark (not fat ice shark, which would be amazing). I liked the Antekadrome fight but I've only done it about 2 times, but the Beotodus was pretty annoying. In general the tutorials have been pretty good, but in this instance I had someone trying to casually talk at me while I'm trying to focus on fighting this guy, but I have a lot of trouble multitasking and missed all of the 'tutorial' bits.
I haven't gotten to see many of the new skills yet but 4 slot decorations seem to drop like candy. Thus far my favorite new skill has to be Guardian which gives you a damage buff for ~15 seconds when you time your guard just right.