"Plant fat sources" is too vague to be useful, because they are partitioned in several classes with very different fat composition:
1. A few "Plant fat sources" consist mostly of saturated fat, e.g. cocoa butter
2. Some "Plant fat sources" have a fatty acid content consisting mostly of oleic acid (mono-unsaturated), e.g. olive oil, cashew nuts, almonds, hazelnuts, pistachio
3. Some "Plant fat sources" have a fatty acid content consisting mostly of linoleic acid (poly-unsaturated), e.g. sunflower oil and most other cheap vegetable oils, many seeds
4. A few "Plant fat sources" have a fatty acid content consisting also mostly of poly-unsaturated fatty acids, but with a large proportion of alpha-linolenic acid, e.g. walnuts, flaxseed and a few others.
The rules for a healthy diet are simple:
1. Most of the fatty food eaten should belong to the second class from above, i.e. plant fat sources with mostly oleic acid
The reason is that this corresponds to the normal composition of the human body fat, so it can be used with maximum efficiency as an energy source or for cellular membranes, without requiring expensive transformations in the liver.
2. Any fat sources from the other classes may be eaten, but in smaller quantities.
3. The vegetable fat sources must be supplemented every day with a small quantity of fat containing long-chain omega-3 fatty acids (DHA & EPA). The cheapest and most convenient way is to use cod liver oil or another kind of fish oil.
Rich vegans can pay 7 or 8 times more for a similar oil extracted from certain algae (algae is the commercially used word; it is not the most appropriate but there exist no more appropriate non-scientific names for those uni-cellular organisms).
4. Heating fatty food should be avoided, because, unlike with proteins or carbohydrates, heating does not have any useful effect but it only degrades the fat, especially the non-saturated fats.
Best would be to not add any kind of vegetable oil while cooking but to mix oil with the food only after cooking and cooling.
Fat that is heated should be of the saturated kind, e.g. butter or lard.