Preamble: My gardening style could be politely termed 'semi-organised chaos'. (The neighbour warns his kids about lofting their tennis balls over the fence - 'it's a jungle in there!' Ha!)

So the daffodils hang out with a sequence of perennials, mostly: Hosta, Astrantia, Saxifrage, Libertia, Clematis integrifolia, polite Tradescantia, Origanum, Athyrium, Thalictrum, and bulbs that flower later such as Tritonia, Freesia, Ixia, Albuca, and the occasional calla.

The 'worst' leaf problem comes, for me, from the very earliest - such as 'Erlicheer' - whose leaves linger until nearly Christmas and they're too big to disguise, so I pretend they're not there and let the Aquilegias, miniature roses, and true Geraniums divert the eyes. (It mostly 'works'...I hope.)

If I use annuals I tend to go for plants such as petunia, verbena, and Impatiens because I am a lazy waterer for the in-ground plants.

The plus, for me, is that the perennials are well-established now and quickly cover the daffodil sites with leaves without encroaching on their actual space; so the soil stays protected and slightly damper - which suits several of the cyclamineus sorts. And they're at rest when the daffs are heading toward the sun.

The annuals usefully provide colour spots and continuity. I'd propose using both.

To answer your first question, how large of a pot are we talking about? The smaller the container, the greater the chance of the entire thing freezing in cold weather. And while daff/narcissus bulbs can tolerate freezing temps in the ground, container-grown plants tend to be a lot more vulnerable. To be on the safe side, you might want to cluster the pots of bulbs together and cover them all in straw, leaves or other type of mulch or tuck them where they will get some protection - an unheated garage or crawl space, under a deck, etc.

As to planting companions for inground bulbs, I also lean towards perennials and especially more drought tolerant selections. When dormant, spring flowering bulbs prefer to be kept on the dry side, so annuals that need a lot of irrigation (ditto perennials) are perhaps not the best choice.