As for how it fares in any real game, AT infantry excels at chasing and microing them between reloads. They are not as good at holding ground. This is totally opposite with PTRS.
PTRS just got their ready aim time massively reduced so that's no longer the case. They will be good at chasing vehicles too now, as well as having good alpha damage (at least versus lights). PTRS has more range too (40 vs 35) so they'll be harder to kite or run away from than other AT infantry. They can't be pushed around when engaging a vehicle in the open. And with 3 PTRS now they can have similar DPM to Bazookas or Panzerschecks unless the latter get pretty lucky RNG (pens for Bazookas and hits for Panzerschrecks).
Hand AT, with the exception of PTRS are about burst damage. The DPM on the penals might be the same as other AT but a misstep in front of pgrens or fussies mean 240 damage off your tank, penals are half that
Bazookas and Panzerschrecks require quite a lot of RNG to deal full damage though. At higher ranges Bazookas often miss or they don't pen, Panzerschrecks often miss. The PTRS always hits. As these small tests seem to indicate, now their DPM isn't far behind the average DPM of the others, or at least their higher effective hitpoints makes up for DPM, as long as the others don't get lucky RNG.
TLDR, the original argument was that they wouldn't be able to fight mediums at all. This is not true anymore, they can be quite a threat now. Not far behind other AT infantry.