A few suggestions. For simplicity sake I'll assume you're focusing with the front standard rather than the back and I'll ignore swing and talk only about tilt since that's the movement you mention:
If your camera has axis tilt you focus on the near and tilt for the far. If your camera has base tilt do the opposite.
How to tell when you've tilted too much: normally as you move the front standard farther away from you (i.e. extend the bellows) things closer to you come into focus and as you move the front standard closer to you things farther away come into focus. When the opposite starts happening you've tilted too much and you need to back off a little.
Whether everything will look "sharp" at the widest aperture once you've properly tilted and focused depends on several variables, there is no general rule, sometimes yes, sometimes no. For example, if you picture a scene that includes a rock in the foreground, trees in the mid-ground, and a mountain in the background, whether you need to stop down to make everything appear sharp at the widest aperture depends on how high the trees are.
The short and oversimplified but more or less accurate answer to your question about the "optimal aperture" is that the optimal aperture is the widest aperture you can use and still get the depth of field you need to make the photograph you want to make. But it's a little more complicated than that. I strongly suggest that you study two articles written by Q.T. Luong in the technical section of this forum. One is titled "How to Focus the View Camera" and the other is "How to Select the Optimum F Stop." If you read those articles carefully you'll know all you ever need to know about everything you've asked here and more.
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