From my short time playing and testing them, there's only a few guns I would have them as a mainstay for.
\- QBZ (it already lacked muzzle device options, which limited its performance as an "accurate" carbine. 30-40 point works best for it)
\- P-90 (there's a lot of space for pricy attachments since it can't run a foregrip and doesn't have a lot of expensive must-haves. 40-point works best, but you can easily get away with the 50-point option)
\- Mini Scout (it works wonders in speeding up your sniper rifles recenter speed, but most require an additional 30-points to rechamber while zoomed. The mini-scout doesn't have this problem whatsoever. big recommendation on the 40-point)
\- All DMRs (Same idea as the Mini Scout, but it also makes spamming more viable at range. 40-point works best for their use cases. Most worth using on the SVK and SVDM imo)
Overall thoughts on each option.
\- 30 nerfing drawspeed on top of additional sway makes it somewhat undesirable for aggressive play unless you're rocking a carbine/smg. Some of this can be mitigated via proactive ADSing (which you should be doing anyways for the chunkier guns), but there comes a point where the slowdowns stack too heavily against you.
\- 40 requires some attachment sacrifices, but the benefits can make it very much worth dropping a pricy foregrip or extended mag for. It's a Lightened Suppressor and a muzzle brake rolled into one after all.
\- 50 requires cutting out too many attachment options that your gun may otherwise need for the sake of improving hipfire for your recoil-reducing suppressor.