I went with standard thin and SS 6115 peaked jumbo frets, the standard thin is thinner than my squires neck, but thicker than my ibanez's wizard, it's actually a good in between that is thin, but allows for scalloping unlike the wizard...
As for if they're a gimmick or not it depends on what your reason for getting them is, mine was ergonomics, I have fatty finger pads that the skin will wrap around the string and rub on the fretboard, by using the scallops with jumbo frets I grab onto the string and only the string and it has made my accuracy go up a bit I've noticed because I'm not getting stuck on the board...
Though keep in mind that if you are heavy handed you will pull the strings down doing somewhat of a vertical bend rather than horizontal throwing your strings sharp. I've noticed this a few times but at least in my case I have to be fairly heavy to encounter this issue...
As far as the conversion it shouldn't matter, regardless of if the wood is there or not the frets are going to be in the same spot whether it be a fender or gibson scale...
I've only had mine on my guitar a couple weeks and after over a decade of non scalloped I wont be going back, it just feels right...
As for the price, replacement fender neck is about $400-$450... My LGS said a SS refret was about $500.00, and the scalloping sites I've found are $100+...
So for a Fender neck you're looking at $1,000 if you want scallops and Stainless Steel frets...
I got all that + A vintage gloss tint finishing for $459.00... Keep it standard, pick the options you absolutely have to have and you can have a really good neck for the price of a fender replacement neck...
It's a really comfortable neck and yes, especially with SS frets the vibrato is silky smooth...