Ok I guess the fundamental question is: is the evo/proto gonna feel stiffer to me than they would for a 5'8" 160 lb guy? if so, why? Im not doubting that it could be true it just doesn't make sense to me. The only reason why I am looking at mens boards in the first place is because NS doesn't make a women's freestyle board for someone my size, so why would the mens park boards all of a sudden feel like planks to me? I have been riding a mens circuit 148 and i can assure you it is a wet noodle after 3 seasons...
If the evo would actually feel stiffer than it is described by a lot of guys it seems perfect, but I just don't want to end up with another wet noodle since I am looking for the happy medium
It's not just your weight it's also your strength. The weight will affect the flex a bit and some handling. Your skill and strength will affect your ability to turn a board.
The SL and Proto are not that stiff. Some freeriders will call them outright soft. In your original post you said you wanted something that can go fast, not get squirrely, and can take in the park. That's what the Proto is.
If you want to sacrifice speed for flex than that's a different story. My own opinion. You can learn how to press a stiffer board, you can't learn how to stop a board from flapping.
But it's your call. If you want something slightly stiffer than the Circuit and don't mind sacrificing top end speed, go for the Evo.
To throw another wrench into all of this, why not the Infinity? It is a directional twin. From what I recall, the flex and shape is twin, the bindings are set back but you can twin it up by adjusting where you mount the bindings. Check on that, but if so, perhaps you just need to stick with the girls Infinity board