The rule for Encumbrance seems to be that you should always arbitrarily divide gear up into two tables. In 1e, weapon encumbrance was listed in the weapons table, while encumbrance for eveyrthing else was hidden in a table in the back of the book.
In OD&D, it’s a similar story. On page 15 of Men and Magic, there’s an “Encumberance” table, which mashes together entries for equipment items (“helmet”, 50 GP weight; “shield”, 150; “weight of a man”, 1750; “miscellaneous equipment” (rope, spikes, bags, etc)”, 80) with values for maximum load (“load in Gold Pieces equal to light foot movement (12″)”, 750).
Then there’s an example of encumbrance in action. A plate-armored guy on foot has equipment that makes him move at the speed of an Armored Footman. Makes sense.
Then, there’s another table, “Weights and Equivalents”, which mixes up carrying capacities (“one small sack holds” 50) with the weights of different pieces of equipment than the ones on Table 1 (“1 flagon or chalice”, 50). Well, fine. But how much does a ewer weigh?
There must be some sort of conceptual difference between the items on Table 1 and Table 2. The stuff on Table 1 is more likely to be the type of stuff you start out with, and the stuff on table two is more likely to be treasure that you pick up in the dungeon. But it’s a fuzzy line.
In my game, encumbrance is an unsolved problem. No one really wants to add up the weight of all their gear. Taking a tip from the OD&D “Encumbrance” and “Weights and Equivalents” table, I can imagine splitting up encumbrance into two areas on the character sheet:
1) Equipment. Anything, within reason, that players write in the Gear section is considered to be weightless. Only the armor type matters for movement rate.
2) Treasure. Everything you write in the “Coins, Gems, and other treasure” section has weight. If you’re running the kind of game where you can find 500 pounds of copper coins, you’ll need to figure out how to carry it. You can carry 10 pounds of treasure per Strength point without being encumbered.
It doesn’t matter what kind of armor you wear: if you have a strength of 10, 101 pounds of treasure slows you down a notch.
I’d consider using 5e’s Disadvantage here for encumbered characters: while you’re laboring under the weight of all those treasure sacks, you’re at disadvantage, meaning you’re worse at jumping over pits, noticing people sneaking up behind you, and fighting. When a monster pops out, you’d better drop the treasure.