My answer isn’t totally on topic to your question, but I definitely think it still applies.

My collection is 99% succulents so I can’t speak on other plants, but I’ve found most succulents do best in tight quarters or in a pot that fits perfectly. For the main reason, extra soil/mix=extra moisture. Which is no bueno for succulents.

If I’m doing repots of succulents in need I will first check the roots. If the roots are weak and non existent I won’t put in a bigger pot because of the main reason I stated above. If the roots are healthy and abundant I go up about one pot size.

When making succulent arrangements I love the crowded look. The succulents should be compaditable when potting up together. Arrangements like the one below last about a year, two tops before they need some assistance. Whether it be pruning, overgrown, rootbound or whatever.

There is a point where things become too tight. I just repotted the Echeveria below because it was becoming too big for its plastic container. In the pic you can see on the right side the pot is restraining the Echeveria’s new growth.

Before

After

A major issue that could occur with a pot that’s full of plants is there’s very little airflow that can move between the plants. Another issue is the tiny bugs that murder my succulents, like meallybugs and scale have a much easier time moving from plant to plant when the plants are packed so close together. Then in turn the bigger beneficial bugs like ladybugs that eat those tiny pests can‘t easily access all parts of the plant because everything is so close together.

This has never stopped me from overfilling a pot tho;).

Iman, plants can be maintained as healthy and vigorous specimens by root pruning and changing out the potting medium periodically.

Without root pruning, plants will run out of space in which to renew their root systems. It is the youngest portion of the root system that absorbs water and dissolved nutrients.

Depends on how small is small. A small pot may be a huge one for others. Also depends on the plant, the soil, do you fertilise, what light you give it which all contributes to how fast a plant will grow. This is yet another very controversial topic I would say

There is a guy in my C&S club that specializes in small pots, some are the size of thimbles and he has plants growing happily in them. I purchased a plant from him, a Adromischus cv 'Hummel's White'. The plant was potted in a small pot, when I transplanted it, it was all roots in that pot.

To get a sense of how small the pot is, look at the nap on the towel. Also, the hardy cactus is growing in Turface fines. ALL particles are small enough to fit through the tiny holes in insect screen.

Portulacaria in white oak acorn cap ^^

Erodium

Al

bonsai the plant to keep it in small pot

All my plants are in pots that are probably too small since i have limited space (and no money for more potting soil...). They do just fine. Growth is definitely slower but I tend to get more flowers as many flowering plants flower more when potbound. I grow bonsai as well and they do just fine. I recommend root pruning though, just to keep the roots fresh and healthy

I didn't know they made bonsai pots that tiny. :-)

It's important to understand that you cannot have a plant in a tiny pot and under the influence of root congestion that's "doing just fine". Onset of the loss of potential associated with root congestion begins at the approximate point in time when the grower can lift the plant from the pot with the root/soil mass remaining intact and in the shape of the pot. Actually, it starts a little before that point in time, but the "root/soil mass intact" mind's eye image is a good reference point and easy to remember. A root-bound plant might be doing well enough to satisfy any particular grower's minimum standard; but, from the perspective of how much potential is being lost, tight roots can be an absolute disaster, bringing growth to a virtual standstill.

Imagine a plant, growth of which has seemingly completely stalled as a result of root congestion (because that's what eventually happens). When the plant is repotted such that the effects of root congestion are no longer a factor, growth rate and vitality increase immensely, not a little bit, immensely. That increase is an up close and personal look at how much potential was being sacrificed pre-repot.

Since a plant's ability to defend itself against disease, insects, and adverse cultural influences is a byproduct of it's metabolic rate, which will be stalled or nearly stalled under the influence of tight roots, the likelihood of death by biotic or abiotic stress factors increases dramatically when plants are grown tight.

This comes full circle to what I mentioned upthread in my first offering re the perspective from which a person views plant-related matters. From the plant's perspective, tight roots are never a good thing. Even if the grower is using a water-retentive medium and is growing plants tight in hope root rot might be evaded, it doesn't change the negative impact tight roots have on plants ..... and there are other a number of ways to effectively avoid excess water retention w/o growing the plant under root-bound conditions. Since all growers order their priorities differently, their perspective often places priority on a factor other than what's best for the plant (I have arthritis and can't handle larger pots; I love plants and only have 2 window sills, so the pots have to be small; .....). There is no judgement to be made about that, but "doing just fine" from the plant's perspective can be a world away from "doing just fine" from the grower's view.

Al