Re: WTF ?!!
I think that 'real' plate would protect you against a 9 MM round (perhaps not a AP round, but certainly a hollow point).
Beanbags would bounce - as would plastic and rubber
Plate was meant to be worn with a quilted body suit underneath, along with a leather overshirt.
Depending upon the period, the proteciton would run (roughtly) as follows....
Mail (especially over the joints - sometimes a full hauberk),
then a leather or linen padded overshirt
The plate had an additional benefit of being curved - causing deflection in many cases.
A shield provided extra cover.
remember that these were effective at protecting the wearer against early firearms and crossbows/longbows at any range over 100 yards.
As for kinetic engergy, they could survive a hit from a spear on a charging horse.
The Bodkin was partially effective - more at restricting movement or weak points than direct injury. A knight on his feet was relatively safe - when they fell over, then there was a problem, as they often couldnt get up and a peon or an archer with a sledgehammer would finish the job.
Earlier laminar armours would also be quite effective - thats the sort of stuff Alexander the great likely wore - again massively padded with linen undergarments.
The problem would be the weight. Fully armoured (not weapons) would be over 50KG or 150 LBs. so real movement was out.
Metal armours were issued to machine gunners during WW1 (they couldnt move anyway). They were reasonably effective - even against rifles