Weighing is by far the most consistent and accurate way to measure ingredients for a recipe. All the recipes are done in metric and US pounds and ounces for your convenience. There isn’t really a rule other than to say you should choose the units of measurement you find the most comfortable with and stick with that.
Using cups is always a bit hit and miss, there are so many variables between weight and volume it’s difficult to be accurate every time. You won’t find cups used very often on this website simply because I stick to measurements that I know work.
Using teaspoons and tablespoons as measures makes sense, they’re easily to hand and as long as you give your ingredients a quick stir, before measuring them, you will be accurate enough. If you use measuring spoons then it’s always best to scrape the top flat, not pack your ingredients down.
If you’re a confident cook who shuns the scales, I’m with you. When I cook at home I don’t use any formal measuring. I’ve always cooked by eye and it wasn’t until I started writing recipes down for other people that I had to buy a set of scales so you will find nearly all the recipes very forgiving.