Most of us (if not all of us ) have, uses and know extremely well those brands.
Where are you from? Some users here might be able to help you better.
Back to topic, the point is that subbing ingredients, unless you understand the philosophy of the recipe is not that easy, and can’t be done 1:1.
Better off to choose recipes that use the brands you can get your hands on, the three you mentioned all have great fruits, INW it’s the only hit or miss, they either have great fruits (thinking about their shishas) or very poor, FW uses fructose in their base, Capella has many averagely good, but a few staples Sweet SB, Golden pineapple and others.
Just yesterday I’ve pubblished here an original recipe released by the manufacturer that uses Capella Fruits.
Subbing? Understand the profile first, you sort of “see” what you can sub it with (percentages used, type of flavour, is it there to support a layer or a head note, and things like that) , but some of them, you just can’t sub them, FLV Alpine strawberry is the first one that comes to mind.
As a beginner? I’d go for Capella first, widely used, liquid makers use it a lot, wide range and easier to work with.
Second FW, quite a few good ones fairly easy to work with and might sub and improve some TFA’s.
Probably you’d get bettet fruit flavours from INW, but you have to know how to use them (definitely not subs) they can be tricky to use and some of them just lousy, you pick Cherry? Awful, you pick Cherries? Great, or Red for Pipe (good cherry) you see how easy is to make a mistake with INW, and they use alcohhol as a carrier too often for my taste, you have to steep it out.
Let’s not talk about their infamous reformulating and change them from great to something just plain sh** or discontinuing awesome flavours, but as I said, some of them are just great, out of the three, I’d leave it out unless a recipe calls for it, e.g. Malina (raspberry) in a recipe is there for a purpose, Cap’s or FW’s are not the same.
Hope this helps you!