it's been very different!
there's a way to split writers into two groups that I've heard a lot of times: pantsers and gardeners (based on whether you write from start to finish by the seat of your pants or you grow your entire story like a well-tended garden) and I am definitely a gardener. so writing this way, where I can't go back and change the past, has been a really wild experience!
...hence the flashback chapters
it took me a little while to figure out this pattern, but I'm sticking to it now (I even went so far as to go back and add a couple chapters in the early part of the first act to make it all work) - even-numbered chapters are chronological timeline chapters, odd-numbered chapters are flashbacks. that way I get to have my cake and eat it too! I get to be a gardener while also writing chapter by chapter. I get to do my favorite thing in all of writing: make readers go "WAIT WHAT?!" as often as possible, in as positive a way as I can. I love ah-ha moments where everything clicks into place so much as a reader that I want folks who read my stories to have them too ^^
(and there are folks who have begun figuring out some of the ah-ha moments ahead of time as well, which has been really exciting to see from the sidelines as I write!)
I'm not saying I'll write every book of mine this way from now on, but I'm now seriously considering it for way more stories than I ever did in the past. this chapter-by-chapter thing can be pretty fun!!