I'm not sure if this will be helpful or not since you only have indoor space but... I've read about DE being used as a mechanical pesticide because the edges of the particles can cut through exoskeletons of insects. There are several threads on this throughout the forum (just do a quick search typing in 'diatomaceous earth'). Most look like they just put it in the soil. There are also a couple threads on the forum about using it as flea treatment for pets. But where I originally heard of it was here where the rinsings containing the dust were actually sprayed on plants to kill aphids, in this case. Someone please correct me if I am wrong, but the particle size for the 5:1:1 mix is dust to 3/8." So I think you could use the dust from your 1:1:1 gritty mix in the 5:1:1 mix if you use that in other container plants.

I'm not a big fan of cedar mulch. I want my mulch to break down to enrich the soil. And I've found that any mulch I've put down only looks good for one year because the sun fades it out. So even with cedar, if you want it to look good, you'll have to put down a new layer every spring anyway. Just my personal observation. :) As far as the size of chunks/chips, whatever looks good to you- like Ken said, the coarser stuff won't decay as fast. The very fine stuff seems to become compacted by the end of summer and restricts water from passing through it, especially if it's put on very thick.

Usually, the nuggets of Douglas fir don't have slivers. It's the shredded Douglas fir that has many slivers. Hemlock is not 100% sliver free either, but it seems that way since the slivers are very few. Hemlock is almost always a fine texture, frequently ligh brown, and may come in bags. Then there are composts that are made from shedded yard debris, that are dark brown and finer texture than either D. fir or hemlock. The only drawbacks of the composted yard debris, is that it can crust and repel water if it's used as a top-coat. If it's loosened periodically, it's fine. Near walkways, or siding, either the compost or dark hemlock can splash and stick to paint, or splatter on sidewalks and track in for stains on carpet.

I've been using a 50:50 base mix of perlite/ turface for many years. You can easily modify this mix for different needs. Most mesembs benefit from the addition of a clayey component. For me, I just dig beyond the topsoil in my yard for some good dirt. I also substitute perlite for some lava rock and small pebbles. It's a heavier, longer lasting mix which works when repotting infrequently for mesembs. This same mix is my preference for small cactus species like Aztekium, Blossfeldia, tricky mamms like luethyi, etc. "bigger" plants like some Crassula, aloes, aeonium etc. you could add more perlite to lighten big pots. It also makes it safer to leave outdoors all spring/summer/fall with rain. My palms, plumeria and cycads live in this mix too. Floating perlite is not an issue. But it does easily displace with high water pressure like from a hose. Some form of fertilizer is a must. I'm also a fan of submerging small pots with small plants into bigger, deeper containers to help stabilize root temperatures. Practically any healthy plant I've ever had to repot always has roots circling the bottom. I really don't understand the concept of shallow or regular pots. I think the deeper the better. I haven't really noticed any exception. For some species it's mandatory. Haworthias, many cactus plants with tuberous roots. Even Lithops which tolerate a shallow home will grow much better in very deep pots. Pleiospilos too. For anyone unsure or unconvinced, try an experiment. Take a pot with any plant you want, and bury it into much deeper pot for a growing season. Pull it out later and see what you find. Bury an Aloe, pachypodium or most any strong Echeveria or similar in the garden and watch it take off. We would all be great at bonsai, plenty good experience with root constriction and limiting growth lol!