Low head loss in plumbing is a good thing up to a point. As head drops, flow rates increase but so does the power draw of the pump. The peak efficiency of a pump (GPM/Watt) is generally near the middle of the pump head curve.

Another consideration is if you have too little head on the return but too much head on the suction side, you run the risk of sucking in air or worse, pump cavitation.

The only down side of the opposite case (too much return head) is that it reduces the potential flow. So it is best to error on this side which is why most pool plumbing has larger suction pipes than return pipes.

So you really need to match your plumbing system with the pump. To do it properly requires a bit of work which is why most pool builders simply do what they have done before.

If you look at the curves for Richard's pool and the Intelliflow, with the solar off is about as low a head I would go on that pump and with solar on is about as high as I would go so I think it would be well suited for his pool.

Usually 1 - 2 1/2" suction line and 1 - 2" return line is sufficient for most pools. If you have mutliple suction lines from pool to pad I would go with 2" lines and if you have more than 2 return lines, I would go with 1 1/2" return lines.

2 - 2" lines is about the same head loss as 1 - 2 1/2" line.
2 - 1 1/2" lines are about same head loss as 1 - 2" line.

Having said all that, it is much easier to add head to a plumbing system then it is to reduce it as your PB pointed out. So I would always error on the side of large pipes and use ball valves at the pad to control and balance the head for the suction and return. This way you can adjust the plumbing system to get the most GPMs/Watt no matter what pump is put on. Plus, it is difficult to predict exactly how much head a plumbing system will have and is best to measure it after the fact.

Also, post the details of your pool and equipement so we can comment further on the design.

BTW 2 x 45 degree bends are only slightly better than 1 x 90 degree.