JCW tuning box

Guys,

What is the best available tuning box on the market, ideally one a few guys have used on here and good gains while maintaining reliability.
A box is preferable to me than a remap as the car is only a day old, I see a few guys quoting models like F56, R56 etc, don't have a clue what mine is but the car is a 2017 Clubman JCW with 231bhp I believe stock....which is ok but not mind blowing. Looking to safely get to around the 275/280 mark, the car is also an auto and don't think it would handle above 300 as well as a manual....plus it's the Mrs car so nothing too crazy for the dog to get carried about in. Any advice, assistance would be appreciated...cheers.

JB4 would be the one I would use and you have a F54

Jb4 seems to get the most reviews