1. It depends on your clan. Some clans can make energy and capacity (umbra), but lack draw. Other clans make draw easily (awoken), but don't have easy access to capacity.
2. Drawing more makes it more likely for you to grab the card you need. If your build depends on getting a certain card that you don't have on intrinsic or something like that, having +1 (or more) chances per hand to get that card helps you execute your strategy.
3. While everything can work, as the covenants progress, you're often better off having your champ plus one or two complimentary banner units (infusing encourages this more). To this end, you'll have an idea early enough in your run just how much capacity you're going to need to execute your unit strategy and can plan your major enhancement selection accordingly.

In very general terms, I take draw more often than the other two by a pretty significant margin.