As you might have found out, there's many mulches around and the whole concept of mulch and mulching is a bit vague, which is a blessing to those who market the stuff.
It really depends on your goals, plants and location because mulching can be to improve water retention/save what, protection from excess rain, weed suppression, keeping roots cool, protection of roots from penetrating frost, to improve soil quality and fertility, or purely for decorative functions.
From what you've said, fertility and soil quality are important here. Really, you want to improve the soil. Here's some non-smelly and hopefully easy to find or order options:
That's where soil improver comes in handy. This is sold in the big box DIY stores and garden centres. It's a blend of garden compost, composted bark, leaf mould, that adds fertility and structure. You apply it liberally to the surface of the soil, maybe raking in gently, and earthworms will incorporate in.
Composted bark fines are very good. This is usually pine or other softwood bark (biproduct of timber plantations) that is shredded and then composted. It adds fertility, but importantly, in poor soils (be they heavy clay, or very silty sandy soil) they add a bulk of organic matter that lasts for more than a year, creating structure and texture, aiding drainage and retaining nutrients. Melcourt is a good producer that make some of the best, and Sylvagrow is a brand of theirs. Note, this isn't the same as woodchips. Essentially, these are composted woodchips, something the soil floor of a forest would be made out of.
If you forgot (or didn't bother) with mulch, but you wanted to improve the soil in spring as if you did mulch, worm castings/worm compost/vermicompost is very good. Don't worry, its screened, there's no worms in it, but its the purest, blackest, most nutritious fine soil structure that plants adore.
Regarding both, some of the sellers of dumpy bagged composts and aggregates sell it bagged in 50L bags (usually in multiples of 5 or 10) that can then be delivered and carried to the garden without having something standing in your drive way or blocking the street.
I'd also recommend making your own leaf mould. Now is the time of year to start. Just bag up dead leaves with some moisture, or stick them in an outside bin, and leave them. They will break down, and can be added to the soil surface after 6-12 months of just being there.
If you want leaves to be useable more quickly and with less bulk, you can run a lawnmower over the leaf pile, which shreds them down into smaller pieces with a larger surface area.
It also really works well just to leave a layer of fallen leaves over the surface of soil. Nature will have it half broken down by spring, to the point where it adds texture and nutrients to the soil. Earthworms are your friends here. It also protects the roots from cold, which is more of concern with Canna (I know some people use straw over them too, but I think Canna are quite a bit hardier than people used to think).
I have used coir chips before.. Go for bigger blocks not small packs - they are more affordable when bought in 4.5kg packs of 4 bundles. You rehydrate them at home (they become like a 60L bag of compost volume). Whilst they don't have many nutrients themselves, they do create a lot of structure, holding water, but also lightening the soil/adding texture. This is something I usually mix up 50-50% with compost (home or store bought), maybe worm castings (only if I have some) or a bit of soil conditioner, just to add fertility to the structure.. I rake it it into the surface of the soil, and the worms and nature do the rest. These coir chips become like a fine, fibrous material, which is really perfect for a range of things, especially where aerating the soil is important.
Ps. spent mushroom compost is a good idea and in most situations it is great, but be careful as it has quite a high pH (i.e., is alkaline). It would be a huge mistake on ericaceous plants, if you grew them, or if your soil is already very alkaline, then it might be too much.