I have used Navigator 80, 90, 100, 120, 160, 200, 250 grams so far.
The 80 grams is very thin for double-sided printing, it is only suitable for text and never for images. If you write with a pen, it might show through on the other side. In a laser printer, you will have fewer problems, and with ink, if it is only text and the printer has a special black pigment for text, it might work, but usually, you will see the ink on the back, especially if it is dye. Generally, I avoid it even though it is economical.
The 90 grams is the best for simple everyday use or printing plain text. It is still in the thin category but is sufficient for plain text and maybe double-sided if I still avoid it for such use. I have used it if I need a simple one-sided photocopy, and basically, I use it in place of the 80 grams.
The 100 grams is simply my favorite, it is just thick and thin enough for everything. It is suitable for simple prints and also a little color if needed, not for photos but for a little color in shapes or graphs, etc. It is definitely good for double-sided printing. It is the sweet spot, as they say. I use it for everyday prints that I want to keep in a file, and I care about the print quality. It is my favorite, and I make sure not to run out of it.
The 120 grams starts to get thicker, it is not for regular use. You have it for printing with color and images. It is not a photographic paper and does not have any coating, it just has a better surface, and since it is thicker, you can print images with slightly more ink. If you want to print work with good quality and binding, it will make it look more professional.
The 160 grams obviously goes to the thicker side, it is like thin cardboard and is suitable for printing with images or anything you want. It is good for simple print covers or for work that has images with a lot of color and double-sided printing, and you are afraid it might get too wet. Be careful, many printers that only take paper from below might have a problem with papers of 160 grams and above. I have a photo printer that takes them from the back, and I have tried up to 900 grams cardboard, and it had no issues.
The 200 and 250 grams are basically cardboards. Cards, covers, printing work for children to color with markers or crafts that they will cut with scissors to glue together, etc. But here, your printer might have a problem if it only has a paper tray from below, it might not take them or it might crinkle them because it rotates them 180 degrees. If your printer takes sheets from the back like a typewriter, it will have fewer problems, but you need to be careful. If your printer is labeled as "photographic," then it definitely accepts them because there are photographic papers much thicker than this.