I am in zone 7b in Georgia, and the "last frost date" for me is less than four weeks away. If your last frost date is also coming up soon, then you might want the head start that your plants would get from being sown indoors. They will germinate faster in the warmer temp of the house. What you choose to do may depend on the kinds of plants you are planning to grow.

Winter Sowing can give you sturdier plants than starting them indoors, but if the seeds are for warm-season plants, that do best in summer heat, and if they take a long time to get to the flowering stage, you might prefer to start them indoors. Otherwise, you could have a longer wait for your flowers and/or veggies.

The official WinterSown website shows/describes starting seeds in containers outdoors, but when I can, I prefer to put seeds right into the ground.

In my yard, dill, beets, and 'German Giant' radish seeds were sowed into the garden several weeks ago, in cold soil and cold weather. The dill isn't up yet, but the beets and radishes are looking good.

I don't use the baggie method, but I often pre-sprout cool-season crops like peas, back in February, before planting them. I start them in a flat/tray, in a seed starting mix, and transplant them to the garden on a less-cold day (we usually have a week or so of warm-ish weather near the end of Feb.). This pre-sprouting saves the seeds from rotting in the cold, wet ground. I would guess that the baggie method gives a similar result.

This probably isn't enough to answer your questions, but it may be a start. Best wishes for great gardening!

-Amy