I've done still strawb wine a couple of times, delicious.
To do sparkling just bottle before the gravity drops too low, and make sure to use bottles that can handle the pressure.
Per gallon, I use 4lb of strawbs, 2.5lb sugar, some tannin, tsp citric, nutrient, yeast (probably best use a champagne yeast for sparkling, but they should all work), and pectolase.
Mash up the berries and leave with the sugar (and a Campden) and a bit of water in a bucket for a couple of days, stirring now and then.
Strain to your fermenter, add the rest of the ingredients, any extra water it needs, and pitch the yeast.
I do find the straining awkward - pulp gets through whatever I do, and the last batch still had some in the final bottles.
I've only ever done sparkling by accident, so can't really advise what gravity to bottle at. I'd be tempted to ferment right out then prime the bottles as I would with a cider or ale.
