Not that we can trust all youtube personalities, but several have mentioned that angled foregrips are okay on pistols. At least until the atf changes the rules again.
I trust the various YouTube gun personalities very little. Some can barely speak English. I seek out and collect every ATF AR pistol letter I can find to try to keep up with the latest.
It's been such a mismash of letters involving OAL, LOP, vertical (so 90's)/angled/upside-down/backwards fore-grips, what's a brace, what isn't a brace, what colors braces can be/not be, etc.
I have yet to see someone shooting an AR pistol one-handed with the brace against the cheek, so why have the brace? If shooting with the brace is OK the ATF still has to consider that you can shoot an AR pistol with a hand on the pistol grip, a support hand on the hand guard, and braced as still legal.
Folks have been shooting silhouette and T/C Contender pistols for decades by using both the pistol grip and hand guard for support for decades. The AR pistol hand guard is no different than those.
A hand stop is very useful to establish a reference point for a hand vs. being an actual support element for shooting, and so far I haven't seen them mentioned in ATF letters.
The controversy on AR foregrips (not handguards) has been on OAL that relates to the ATF definition of a concealable firearm either as a AOW with <26" and a foregrip, or not with an OAL
> 26" which is generally not considered concealable.
All this continues to be as clear as thick mud, and at least ATF has slowed down with their various letters.
The only sure thing is we're lucky we have Trump or AR pistols would cease to exist.
My .02