On the VF-1, I like them with our without FP or GBP, I like'em both ways. On the VF-11B my opinion is the same. When it comes to the YF-19 or YF-21, I really think the FP could have been bigger and more noticeable. Something big and aoutrageous would've been perfect. Presently there almost no difference in this last two with or witout FPs.
On the VF-0S, the Ghost booster is not particularly my favorite. I'd rather see some modular/structural attachment that would enhance the design of the Valk while increasing it's functionality. The Ghost booster to me is like a quick fix. Similar to that booster rocket attached to the VF-11B in M+ to keep up with the YF-21. It is like SK didn't have time to design something better. This is how I feel when I look at it: "looks like there's some tubular thing on top of that aircraft...Wow, it has a big @$$ rocket, wow it goes faster... Not amused, not easy on the eyes.