- XP - Spell components that don't have a gold value listed - Encumbrance, except when the campaign has survivalist elements and it is thematically appropriate - distance to a target on a hypotenuse: I just use the bigger of the X and Y - initiative for every monster. Mostly enemies moves on the same initiative, except for bosses. Anything that joins combat in progress does so at the top or bottom of the initiative order as necessary.
Not sure if this is what you're interested in but I also don't bother with plot or adventure or campaign design. I do extensive (pathological?) world building and NPC design and then just start the thing running. We uncover the plot at the table.
@evilchili I mostly do the same for stories, the world is build, and Things Happen, I follow. xD Also same for XP, I don't bother with is, leveling up is with things accomplished in the story.
I do like the idea for initiative, would be less cumbersome to manage.
@transcendentempress Stacking all combat into "players go, then enemies go" has a lot of knock-on effects you have to be careful of. If enemies get to go first random enocunters can become deadly in a hurry. On the other hand a well-oiled player machine can destroy an encounter in a round or two. My players are mostly not interested in tactics so this hasn't been an issue.
I also have 6 players which means I minimize the wait time for each one to take a turn. I rely on lair actions and legendary actions (even for low-level critters) to keep combat from being a slog.