Batteries for your mod are a matter of budget,choice,confidence, and a smidgin of common sense. I've used 'cheap and cheerful' unbranded, and more expensive 'named and recommended' brands, both protected and not protected, none have performed,in a mech, any better,or worse,than others, and I've had the odd DOA with both cheapos and dear 'uns, which is understandable seeing as the vendor is only selling 'em, not making 'em.
As for button or flat top, it's the one that fits that's the right one, and most mechanical mods with adjustable positive pins, have margins for both. Having said that,with the mech you have chosen, the PH22, I would opt for flat top, seeing as you won't be able to adjust the top pin,but you are able to stretch the bottom spring a tad if the battery is a bit on the rattley side.
