There isn't one answer. Every oil is different. Some, like corn, have only Omega-6s. Given how common corn products are in many countries, this is a problem. Other oils have a significant amount of Omega-3s, such as flax, canola, soy and walnut. One thing that is certain: consuming the "good" oils is better than lard, tallow, shortening, butter and margarine, all of which are high in saturated fats, as well as cacao butter and solid oils like coconut and palm. Note that ruminant animals' fat naturally contains trans fat.

Sesame seed oil has also been around for thousands of years, and I'm willing to bet that there are more.

Let's keep in mind that olive oil is from the flesh, not the seeds, but peroxidation still impacts it, albeit not as quickly as walnut oil, for example. How should we classify coconut and other palm oils? Coconut oil comes from the flesh inside the shell and is typically extracted through heat, which causes it to separate from the "creme". I'm not sure what the traditional method is to get the creme from the flesh, but I believe the flesh is grated and pressed. Unfortunately, what I've seen for the saturated fat content of these herbaceous trees is that it's not good for health as a food, and the same is true of corn and safflower, and some of the others. Palm oils tend to be from the fruit, too, but I've never seen it processed nor do I know what part they come from. Palm kernel oil is worse than regular palm oil. Any oil that is solid or semi-solid at room temperature is high in saturated fats and bad for health, including butter and margarine.

One thing that's important to remember is that oils break down due to peroxidation, so it's important to not collect bottles of it and let them sit for months or years. Only buy what you need in reasonable quantities.

Processing oil with cold-extraction such as pressure is the ideal way to extract oil, as it does the least damage to the oil. Processing with heat results in the production of trans fat, which is why deep-frying in the same oil again and again is bad for health (think French fries, onion rings, donuts, etc), and those oils are labeled "refined".

Recently, my sister has become convinced that seed oils are bad (she is an idiot when it comes to health info and very vulnerable to being manipulated, sadly), and I heard her say that Canola is the worst and was created as an engine lubricant. That is not exactly true. Rapeseed oil has been used as an engine lubricant, where the high erucic acid doesn't matter, but Canola is a food-grade variant that is low in that acid and, thus, safe for the heart. Non-food rapeseed oils, called colza oils, are not in the same category as Canola and low-erucic-acid rapeseed oils. Canola is one of the best oils to consume, especially for high-heat cooking as it doesn't break down as readily and doesn't produce trans fats as easily, either. Olive oil is great except for high heat. Some other oils are also wonderful but break down quickly so it's best to buy small quantities to use rapidly. Oils with vitamin E in large quantities are less likely to produce trans fat when heated.

Some of the best oils are, in descending order of Omega-3s content: linseed/flaxseed, hemp, walnut, canola, soybean, mustard, olive, avocado and pumpkin. Other oils can also be included, such as kelp, algal, and Perilla. And, of course, there are several sea animals that have good oil in them, primarily prey fish like salmon. Eating predatory fish, even if it's got good oil in it, carries high risks because of the bio-accumulation of toxins like DDT, PCBs, PFAS and mercury, so avoid swordfish, marlin, grouper, tuna, shark, etc.

I wish you would've delved farther into the large amount of research that's available about seed oils. If you had, you would've been able to find the answers to your questions, and that would've helped your readers. To answer the question you had about whether or not increased insulin resistance could be beneficial, that is definitely bad. Insulin resistance comes about through a complex process involving lipids (fat) in the same cells where glycogens (sugars) are stored, taking up the space and thus requiring excess insulin to be produced so that the glycogens can get into the cells. That's grossly oversimplified, though.

Finally, on the YouTube channel "Nutrition Made Simple", Dr. Gil Carvalho looked at some research into different types of food frying materials and the research says that while you'll be healthier consuming the good oils, the best choice is to not consume oil often. I also recommend the channels "Viva Longevity!" and "Physionic".

In conclusion, some oils are not seed oils (coconut & olive); some oils are good for health because of relatively high levels of Omega-3s; and some oils also contain vitamin E, which seems to retard the breakdown of oil with heat into trans fats. Those which are solid at room temperature should be avoided, just like animal fats. If you can minimize the use of all of these substances, it's better for your health, but that means you'll need to avoid fried food at restaurants and bakeries, which are likely to have lots of trans fats.