Welcome to the forums! and welcome to "Club Ssassy" fellow sass owner. When the time comes, you will find that your choice in suppressor will dictate what muzzle device you use as each manufacturer has their own proprietary design. The device can be a brake or a flash hider and is customarily included with the purchase of the suppressor, but not always so you will have to check. Although less popular these days, there are simple thread on suppressors that attach in place of a flash hider or brake. These typically are meant to remain installed except when cleaning or casing the weapon and a simple thread protector is all that is used when the suppressor is removed. The hassle of switching between suppressor and a brake or flash hider is why most suppressors these days are Quick Detach.
Stay away from hydraulic buffers. They have a history of high failure rates in AR15's and I have no reason to believe they would last longer in a .308. They also bring nothing to the table in terms of recoil reduction. As it stands your weapon has a recoil impulse that ranges from 7ish - 10ish ft lbs of recoil energy depending on the ammo used. So it is kind of a non issue. A suppressor or a muzzle brake will reduce some felt recoil though, if that is goal.
Upgrades are a matter of personal tastes at this point as you have one of the most complete out of the box rifles I've ever owned. I replaced the factory match trigger with a Geissele DMR adjustable 2 stage. This is a truly sweet, great shooting trigger.
I replaced the PRS stock for two reasons. The first being, while well intentioned and well made, the adjustable cheek piece is uselessly too far to the rear for me. This had to be done to clear the charging handle and really can't be helped. Secondly, at it's shortest settings it was still too long for my kids to shoot the rifle comfortably. I switched over to the MagPul UBR stock and could not be happier. If that sounds like something you would like to do, just let me know and I will walk you through the process.
Good luck enjoying your new rifle, now try a box or two of everything and find out what she likes best.
Here is my baby, complete with red neck shootin' mat.
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