You can typically mix plants that are in the same genus together, as well as plants that have similar lighting and water requirements. It is important to observe the plants as well, because you can determine if they are suffering and replace them with more appropriate ones. Succulents such as lithops have to stay on a weird watering schedule, so it is not usually advised to keep them with different plants. Stonecrop sedums and sempervivums usually do well with one another, and echeverias and tender sedums make a stunning pair. If you are worried about overcrowding, plant the succulents with some space between them.

Kara has shown some very nice combinations, but you are in z6 and I would suggest not to pot together hardy succulents with tender ones - unless you like lots of repotting! Semps and many hardy sedums should grow outdoors whole year round, so you would need to separate them again in late fall. But potting few hardy ones together works well too and they should just stay outdoors for the winter - I have some in wooden boxes and they look good - IMO :) I put them just outside of windows in winter and enjoy them that way.

Really nice arrangements Kara, love the color variations.

Good thought, Rina. Thanks for pointing that out! I don't think I have many hardy plants currently. Are sedum lineare and reflexum cold hardy?

S. lineare is supposedly hardy to z6 - I have one and it struggles in my zone which is colder, ots of it dies but I always have some coming back to life. I believe S. reflexum is hardier - it overwinters for me quite well (Angelina and Blue Spruce). And there are many hardy sedums, and number of other hardy succulents. Some can grow quite tall - like Hylotelepiums spectabile; others more of ground covers - like S. spurium (few different colors).

Beth I was under the impression you are keeping your plants inside in the winter. Most of the plants I've seen of yours I are not cold hardy.

Sedum lineare 6a.

Generally the chubbier the leaf the faster they will turn too mush in the cold;), but can handle dry and hot climates easier. These chubby leaved plants can go longer without water. The thinner the leaves the more cold hardy, but usually need more water to stay looking nice when it's dry and hot. Take this with a grain of salt though;). This is just what I've noticed.

Edit: the statement I made is a general statement. I was just thinking about if you got a Euphorbia milii which has thin leaves, and would be a soggy rotten mess if left outside in freezing temps.

Kara, you're right. My plants are staying in this winter. And I do think I only have 2 cold hardy plants, two semps. Btw, your plants look amazing. I hope I can get mine to be just as nice.

That's what's nice about this forum. You can learn from all of our stupid mistakes. Maybe I should speak for myself;). My stupid mistakes. Best two things I've learned know your plants, and this one Karen is always advising. Leave your propagations alone. It totally does slow everything down. Constantly disturbing and checking slows everything to a halt. You wouldn't think, but it does. Plus you are increasing the risk of ripping out brand new roots. Just let it do its thing;). This goes with plants that aren't even being propagated. Most succulents don't like being fussed over.