So I just finished binging all 9 volumes of the LN of Lazy Dungeon Master and I was too lazy to wait till May 5th for the 10th volume so I planned to just read the WN instead. I wanted to know whether I should read the WN as if it was completely separate from the LN or if I could skip to a certain section where the LN starts to diverge from the WN.
IIRC there were some changes when it was published as a LN, with some being: 1. Meat (Kuroinu) not being used as 'Meat' 2. Rukoro(or what's her name) being in the 'age up' form more often (In the WN, she starts out in the loli form, and later the 'age-up' is revealed). 3. Also, she comes along when they went to the village, to by that other one, instead of staying behind. -- There were other changes too, but can't remember them off the top of my head. Personally, I'd probably just read it as another series, with a similar premises.
The first 5 volumes are more or less the same with some LN-only things added like the second hero of vol 3. From 6th onwards the LN expanded some arcs significantly and vol 8 was practically entirely new. Otherwise LN is the usual better fleshed out version of WN with some minor differences. The major diverge starts at WN chapter 200. WN chapter 301 is where the story would continue from the current place in LN. That said, Ziru's translation is good and if you really liked the series you might as well check the earlier chapters.
Did you even read the "Afterword" ???. The author clearly said that the story changed track from 2nd vol and for latest 9th vol the difference is about 80 to 90%. Try reading all the afterword it's only 2 pages long.