Yes, both models CAN have their fabrics removed and even washed. It is not completely easy, so pictures of how it was are always best. This video could help, too:
With the Maxi-Cosi/Cybex adapters dedicated to this model, you CAN attach a Joie i-Snug car seat, yes.
Though I would not recommend a carrycot - it has a different attachment system so most won't fit, and those that could fit those same adapters might tilt the center of gravity considerably, as the stroller is not made for that bassinet shape and weight. You should be using the dedicated Baby Jogger bassinet for this model to be safe and the push comfortable. And yes, you CAN remove the textiles to have a bare frame plus a car seat/carrycot.