How can i see a preview of how my freestyle line settings will look? i dont care what render engine its in.
The freestyle lines are only created once the scene is rendered. Best thing you can do - as far as I know - is set it up, so that rendering your preview is fast. Try using Eevee, lowering the resolution, etc.
If you’re not in a production setting and willing to use the 2.93 Beta or 3.0 Alpha version, you can also try out the new Grease Pencil Line Art modifier. It was designed to replace Freestyle and allow exactly the kinda preview you want.
It doesn’t provide all features of Freestyle, yet, but there are some areas, where it already surpasses Freestyle. Here’s a nice overview video by the developer: Youtube: Line Art Modifier.
I’d try the 3.0 Alpha because I think it has some speedups for Line Art that are not included in 2.93 
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