Plastic mags? Veprs can easily be converted to accept standard capacity magazines, in the same way Saigas are: add a bullet guide & file down the mag catch. You may also have to make a couple parts changes to meet 922r (swap out the trigger group for 3 parts + a US mag and you're compliant).
Warranty? For an AK? What for
On the comparison of a Mini-14/30 to a Vepr: I'm not putting down Mini-14's (former owner here). The changes Ruger has made since the passing of Bill are welcome to a great American company; however, Vepr is THE top-tier AK known for their accuracy and durability. Period.