I captained for many years, and there is just no good answer. You can't know whom the other team will play, at what line, and how their strengths/weaknesses work with yours.
That said, what I would do is set expectations early and then switch it up later. So round one, play according to strength. Round two, play according to strength. Once you reach the semis or finals, switch it up and stack.
My other rule is that I avoided having singles players play more than one match a day. A weaker singles player is a better bet than a strong singles player who already played once that day (unless she had a super-easy match, which rarely happens in playoffs).
My last piece of advice is to take it easy. I don't think it works well to put a lot of pressure on your players. Those who are already competitive people and fired up do not need you to fire them up. The ones who get nervous and tight will get nervous and tight if you try to fire them up.
And if you don't know your players well, ask them if any don't appreciate having teammates watching them play. I had some ladies who would get tight if friends watched them. I don't get it, but that's how they were so I would not go watch their matches.
