I installed Chunky 1.3.53 and Chunkyborder 1.1.43 using CurseForge for 1.19.3 and the trim command doesn't seem to work. All the chunks outside the region I specified do not disappear and I can still interact with them like normal. Also in Chunkyborder, I can pass through and teleport outisde of the worldborders I set with no resistance. Am I missing some commands or something? How do I make the trim feature work properly and the world borders impassable?

Trim can be a bit confusing. Have you read the section about trim on the FAQ? If you are currently loading these chunks they will not be deleted.

Additionally keep in mind chunks deleted by trim will be re-generated again if you visit the area they are in. If you don't want to generate them again do not go back to the area you trimmed. Set up a world border to prevent players from accessing those regions.

If you need further assistance with this please join the chunky support channel on our Discord server.

Ah ok that makes sense, thank you. Still, like I said, the world border isn't 'hard', I can literally walk right through it. Is there a way I can make it so I can't bypass the world border? Also to clarify I'm playing on a singleplayer world.

Vanilla world border supports hard collision so you can use that if it's an option.

For chunky border & especially non-square regions, there is no hard collision support. You can change the check interval in the configuration from 20 ticks to 1 tick which makes it as close as possible to being a hard border (it will teleport players back within 1 tick of passing). Alternatively, pad your border with a few chunks if the only concern is a web map like dynmap being pretty (or better: set a visibility limit so the areas past the border aren't rendered on your map).