Whenever you feel you can handle them. The earlier the less disturbance to the root system (because it hasn't developed much).

If you feel you can, I often transplant as cotyledons or first set of true leaves. It's up to your skill of manipulating the seedlings (and their innate size, I'd never do gesneriads or begonias at first true leaf). I'd say yours are quite large seedlings.

You can start fertilizing after a few days to restablish the plants, water weak solutions, don't burn them.

I'm heavy handed so if I try to pot up when they're tiny, I use a fork to hold them. Otherwise I tend to crush the stems just by touching them. I think you're supposed to wait until you have 1 or 2 sets of true leaves, tho.

For most things I like to wait until they have two true leaves, not counting the cotyledons. If you want artichokes, get those outdoors as soon as you can get them potted up and hardened off. Most varieties (not counting Imperial Star which was bred to be an annual) of artichokes need some cold temperature exposure as plants or they won't produce the first year. Keep their growing medium moist but not soggy and only fertilize your young seedlings with a very gentle fertilizer---I like to use Fish Emulsion at regular strength. If you use a commercial water soluble fertilizer like Miracle Grow, only mix it up at 1/3 to 1/2 strength so you do not burn the roots.

Thank you all! I plan to pot them up this weekend- most are only a week old but are already starting to get their first true leaves.

Ya’ll rock!!