I prefer the first, it draws the eye into the center. The other one my eye wants to wander to each of the four corners.
For the half rectangles .... you can do them just line regular HST's but you have to remember to offset the center line 1/4" from the center - opposite side of each corner.
IOW ... on the top of the rectangle mark a line 1/4" from the upper right corner. On the bottom of the rectangle mark a line 1/4" from the lower left corner. Use a ruler to match these marks and draw a line dissecting the rectangle on the diagonal. This is now your "center" line - like you would draw on an HST. Now mark your 1/4" sewing lines on each side of the center. Sew, then cut down the center line. Just like HST's you will have tabs on two corners to snip off.
There are also HRT templates you can buy, or make if you prefer a template method.