Well with out context all things has some level of a performance hit that can become an exponential if overused and the need, ie with in context, of having 30-60 NPC’s on screen at the same time using morph targets I would say is a performance nightmare in the making.
A morph target is “unique” to the target mesh so unless applied to a single alpha character each and every NPC would need a matched morph target. IE if you have 60 NPC’s that needs a mouth open target then you would need to make 60 targets for each NPC.
For each character that needs a dialogue channel will require the full set of morph targets available as part of the export for the purpose of receiving authored animation data.
With 4.13 it’s now possible to included animated vertex data but there is no information that vertex animation is now GPU rendered unlike the standard of morphing data being CPU rendered. Generally the GPU only supports skeletal transform and rotation data so before you even hit 30 NPC’s I ould suspect that the FPS hit would make the game unplayable.
The memory footprint allowance for each character added will also be exponential in growth that even if hardware rendered could exceed the memory limits of the GPU.
That being said the question of adding the targets is not an issue as compared to the need to author the desired animation shapes as a data set and it’s the target shapes being animated that can become a further performance hinder to efficient work flow.
My educated opinion morph based animation is only suitable for non-game critical needs and limited to low detail mesh and not used as part of the primary character animation design.
A better option for video game facial control have a look at cluster or marker shaping.
As for live real time morphing this is on my list of things to test with 4.13 now supporting vertex based (aka point cache data) animation so the actual provable performance hit should become easier to prove or disprove but once again the maintenance cost is to high in my opinion.
P.S. Looks like morph targets are now hardware rendered in 4.13