Replacing the Larue factory pistol grip with a magpul on my 16” DMR
I want the grip core storage.

I see lots of vertical grips on modern chassis’s
Is it worth checking out a magpul K2 grip which is advertised as a steep grip angle for small PDW guns?

I've always liked the K2 or K2+. Have a couple of the wide ones as well, more towards vertical than the two previous mentioned. All three fantastic IMO.

K2 is good to go if you need storage.

All my AR's wear a Fab Defense Gradus.  Near vertical, rubberized, only draw back, no internal storage.  I tried an Ergo TDX-0, but it doesn't give enough room for your middle finger, it always crams it into the trigger guard and is uncomfortable.  You'd need that area relieved (and there's not much meat there to do that).  It's also a fat grip (which I like), but the finger clearance is a problem, so that's why I use the Gradus.

I like the BCM grip, have put it on several ARs.  It's pretty vertical.

I’ve never liked magpul grips. If you want steep PDW-style grip, Die Free Co Kung Fu grip (currently no grip plug option but “coming soon”). If you want near vertical precision style grip, Driven Arms Co crossover grip, with or without beaver tail and has a storage floor plate option.

Have both, like both.