You should cut off dead leaves from plants as they are not doing the plant any good and could actually hinder the process of the plant growing new leaves and thriving.
Although the plant will adapt and eventually grow new leaves if it's not dead as well but it's best to remove any dead leaves from the plant or any damaged or yellow leaves from the plant as well.
You should cut the yellow leaves off of plants as the yellow leaves are technically dead.
The yellow leaves are sucking nutrients from the plant that would otherwise go to thriving and healthy leaves.
Leaving the yellow leaves on the plants means that wasted energy is going to the yellow leaves.
Once the leaves are yellow on a plant, the leaves are technically dead and there's no point in really leaving them on the plant.
You can leave the yellow leaves and they will eventually probably fall off.
But if you want the plant to thrive it's best to cut the yellow leaves or other dead leaves off and allow the energy from the plant to reach the newer leaves or help grow new leaves.
Some people recommend leaving the yellow leaves unless they are severely damaged or brown as the plant is actively pulling nutrients from the yellowing leaves to use elsewhere which can sometimes benefit some plants.
However I find it always best for me to cut any yellow or brown or damaged leaves from the plant and doing so my plants have always thrived much better and grew new leaves much faster.
Yellowing leaves are also a natural part of a plant's lifecycle and as the plant ages the plant also will reabsorb some nutrient from older leaves and use them for new growth.
For some plants removing the yellow leaves could prematurely hinder the natural process of reabsorbing the nutrients and could stress some plants.
But in most cases it's fine to remove yellow leaves from plants if you prefer to do so.
Also remove any leaves that are brown completely or severely damaged or leaves that are starting to rot out.
Or if you see any signs of disease or pest on the leaves or plant, isolate the affected plant and remove any damaged or diseased leaves.