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As stated, it all depend on how you trim them. They are just beef back ribs, the only ribs worth eating! Depending on how thick, 275°, bone down for about 4 hours and they should be wonderful!
15-20 minutes a pound to get to 125 but that depends on what temp you start at. If you want more smoke, put it on right out of the fridge.
My is to sear outside first then slowly bring internal temp up to desired temp. My thinking is if you slowly bring internal temp up first you risk overshooting when searing the outside.That's how I cook mine.Mudflap
Only sear first if you want a thick layer of gray, overcooked meat.
The end result of the prime rib was that it was great.