House rules actually in play: single page "player's aid", front-and-back, condensed and summarized. Probably a quarter of which is "cool things you can do with a Critical Hit, instead of extra damage".
Rules in a word document that I consider "officially part of the campaign" - 20 or so, because after 40 years of playing many games (cough "Magic: The Gathering" cough), my friends and I are all rules lawyers to some extent, and I like to be verbose to eliminate misunderstandings and clarify edge cases. House ruling Falling Damage, for example, takes 3 bullets to say ("d10, cumulative, Acrobatics for half"), plus 6 extra bullets to handle definitions, edge cases, Monk slow fall, different size creatures, etc., plus three examples. House ruling Counterspell into a class ability is simple to say, but takes two pages to describe, define, and address interactions and edge cases and special rules, as well as a paragraph on "what was the intent of this massive change".
Rules I think are cool and I'd like to have in the game: Um... what if I just count the number of documents, instead of the pages? ;-) Heck, I added three more items to one of the docs just reading through this thread (Medicine/Surgery healing d4s, for example). Spell or feat clarifications/tweaks tend to end up in this category. For example, "Power Word Kill does 100 necrotic damage, and instakills if it reduces you to 0 hp." But... the party is 6th level, so this "rule" is not in the "officially part of the campaign" document because they will likely never reach 17th!
Plus three Excel documents for cataloging and categorizing diseases, expanded weapons and armor lists, and one for special materials/abilities and crafting. Lots of columns, lots of rows... and I think now three lines have made it into the game as unique effects.
Homebrew: New spells and items have their own documents, culled from internet/reddit sources and my own creativity. Just available as a reference. Plus setting specific changes - my campaign has no gods or other planes, and a sharp delineation of arcane vs. primal magics. This makes for small to large changes to some classes, reskinning of some subclasses, and elimination of some subclasses. Plus some classes get changed lore - alchemists and artificers are from the Empire, wizards are from the Northern Kingdoms, all sorcerers are "genetically dominant" (i.e. any child with at least one sorcerous parent will be a sorcerer) nobles called "Mageborn", druids are barely tolerated in "civilization" because they use "goblinoid magic", warlocks are anathema (neither Mageborn nor "Tower-trained"), and so on). That's... about 30 pages, I think?