Kiniki have been around a long time, I remember seeing their small ads in the (Sunday) Observer in the 1970's.
In the 1970's there was a fashion for high, narrow waists and Kiniki did not change their styles for a long time although fashion changed to Arena and Japanese style low waists.
Kiniki seem to have concentrated their development effort into tan through fabrics.
The Kiniki Brazil is an old design with a high waist and a cut away half back showing a lot of the sides of your buttocks.
The Kiniki Riviera again is an old design, similar to the Brazil but with a 3/4 cut away rear, displaying some of the sides of your buttocks.
The Kiniki Eden is a more modern design with a lower cut waist though not as low as the Japanese styles, the waist is less than 2" at the sides so is a bikini rather than a racing brief.
The Kiniki Andre is similar to the Eden with a lower waist than the older designs but they've cut away the legs to make a 1" side and less than full coverage at the rear.
It's up to you to decide whether you preffer a high or a low waist such as Desmiit make:
https://www.ebay.co.uk/itm/Mens-Desm...mvR6 ODprC8vQ
Then decide how much you want the rear cut away full, 3/4, 1/2, 1/4 or thong. Once you know what you want it's easier to choose.