Not as much of an effect as you think.
Doing some back of the envelope physics calculations:
A M1 Abrams tank shells weigh around 18 kg.
Modern capacitors have a max energy density of 9.5 Wh/kg.
* Assuming all of that shell is capacitor you get a maximum energy released of 171 Wh or 640kJ.
The math would get even worse if you only considered the mass of the projectile.
To put that in perspective; * Setting off ONE kilogram of TNT releases 4.6 million Joules of energy. * A .50 BMG bullet produces between 14kJ and 20Kj * There is more power in chunk of C4 the size of a deck of cards than in your 18kg tank shell.
Real world plasma is very different than the plasma you get in sci-fi. To quote @GrumpyYoungMan;
Plasma isn't special, it's just ionized gas, usually at high temperature but not always (see en.wikipedia.org/wiki/Nonthermal_plasma). Even conventional HE produces plasma (e.g. 435
https://www.researchgate.net/publication/336015137_Study_on_Electromagnetic_Radiation_Generated_During_Detonation which discusses RF generated by plasma during HE detonation) so one could say that HE shells are already "plasma explosives". Any damage caused would be because of the high temperature and kinetic energy of the gas, not the ionization, just the same as regular HE does.
Are you sure you need to do calculations based on your (I'm guessing, limited) understanding of physics? Pretty much every established sci-fi IP that uses plasma weaponry has handwaved the physics and said "Plasma weapons are effective." For instance the super cool bolter round cutout images in 40k don't derive effectiveness from physics. In the game the effectiveness changes as the game gets rebalanced. In the lore it's as effective as the story needs it to be.
My advice is when in doubt do what is cool and trust your audience to care more about your cool story, film, comic, or game than they do about doing physics homework. In fact if someone cares enough about your work to take the time to point how you got your math wrong that's a sign that they care enough about it to obsess over it. 477