I have a both a double stack r1 and a para p14 both in 45 acp. The Remington mags fit in the para, match up perfectly. They hold 15 rounds, but the magazine is FULL with 15 rounds and you practically have to stand on the gun to get the magazine to seat with a full mag and the slide closed. So really 14+1.
The r1 has Checkering front strap, is made of stainless and has some flat black finish that seems to hold up well.
The r1 takes para barrels, grips. The r1 has Novak sights where the para has their own cut. I had the front para sight cut for a Novak but the rear has to remain a para.
My R1 is a tack driver, but I did have to replace the extractor as it was cut on an angle when installed. Also the accessory rail wasn't cut well and wouldnt hold my TLR-1, so i had to file it a bit. Like the frame moved when they were machining it or something. I hate that i had to do that to a 900 gun, but I don't mind tinkering a bit.
So to answer your question, it is basically a para with minor changes.