I've always just loaded the Lapua brass and shot it out of the gate.
A lot of my Lapua brass has come from factory ammo, as well as virgin brass.
If you want to keep the smaller flash holes, you need a small decapping pin for however you de-cap.
It's great brass and more economical in the long run. Used to be able get it for $66/100 from AA before the new Lapua/USA price hikes on it.
I load and shoot it and Hornady brass equally.
Accuracy loads are most common with 8208XBR, AR-Comp, BL-C(2), and CFE223 under 107gr to 123gr.
I've shot mostly AMAX over the years due to price and performance, but the 123 AMAX has been replaced with the 123gr ELD-M, same AMP jacket, same core uniformity, improved BC, new tip (which doesn't affect things for Grendel other than less tip deformation from impacting the feed ramps).
With 8208XBR, don't exceed 28.5C grains under a 123gr cup and core bullet. Hodgdon's data for that under the 123gr SMK hit 50ksi.
I personally load a lot of CFE223 under 123gr AMAX and just ring steel with it. I typically see rapid-fired groups under or at MOA at 500-1000yds even from shorter barrels, but I'm at high elevation too in my region. My go-to mass produce load is 31.2gr of CFE under a 123gr, which is .7gr away from max in my chambers and the pressure trace rifle we used for checking these things.
I don't like wasting my time at 100yds, or even 500yds-and-in because it's just not challenging for me shooting those distances, so I like to put my 12" poppers at 700yds, and IPSC steel sils at 900-1100yds. When I put my 12" poppers at 400yds, the rounds just impact into the same splash zone on the steel, so you can't distinguish one from another through rifle optics at 10x anyway.
6.5 Grendel Knocking Down 600yd steel, then rapid fire on 500yd