my stbxw isn't a high-conflict type. she's very passive/aggressive. she and her family have an arrogance problem - they don't create drama, they act unilaterally and leave others to pick up the pieces. for a long time i was terrorized by what she could or might do in the divorce, but i did not suffer the horrors that some others here have suffered. no false accusations, no theft, and, in the end, no negotiations and no court either - she took the first offer i made. i feel sheepish mentioning that. so i did learn one very great lesson:

to make sure that everything is as fine as it can be, you should prepare to the best that your finances will allow, so get a good lawyer. my answer to the question
What is the best approach for being assertive and not inciting conflict?
is to have that lawyer (that pair of lawyers, assuming your SO will also have one) between yourself and the other party. and after you serve (or are served), end communication as far as you can entirely. i cannot tell you how much it changed my own approach. emotions were so hot for a while, i was so FOGgy, that if we had gone to mediation i could not have
asserted, i would have either caved, leaving me hating myself, or flailed, falling into the "angry man" stereotype. but i found a meticulous L, and since i was dealing with her, and not my w, i was able to lay out what i wanted. she's a cool as a cucumber, never taking bait, never getting insulted, and when the other side got demandy, she just laughed a little. (she isn't perfect, she doesn't communicate as quickly as i'd like.) so i was able to feel comfortable fashioning an offer that was outrageously in my favor, since i didn't need to fear my w's reaction.
the lawyers have a different set of priorities from the parties divorcing.
- they're a community and they want to keep on terms. my wife's L has a name as a toughie and i was surprised when my L said "i'm sure we'll be able to work together."
- they have reputations to maintain. they're supposed to advocate for their clients, but when it comes to the crux, they're not going to suggest harebrained ideas (at least, they shouldn't). my w and her L blew smoke after we exchanged net worth documents but when, two months later, i made the offer her L must have told her just to take it.
- this is civil court, not moral court. this was a hard one for me to swallow. i wanted to file in adultery (still on the books here in NY) but my L kindly but firmly put me off it.
- this isn't their divorce, so they're not going to get bent out of shape about what you're going through, although they should be kind (mine was, patient too).
all of these things will reduce the atmosphere of conflict. an "at-torn-ey" is someone you "turn (your case over) to." they're supposed to put distance, and that reduces conflict.