No pets allowed in the front seats on Premium Economy, I have tried it already and I was not allowed, i have another upcoming flight in W with AF but on the new seats that recline (if the plane remains as it is), I am not given the option to select those front seats but my partner can choose them ( we are on separate bookings and i have the dog ticket on mine).

On the short flight on the A220, the space is pretty small but enough for your dog bag normally. Here is a virtual tour of the cabin on A220 https://my.matterport.com/show/?m=kCcJuY7MkhD so you can have an idea of the space.

Having flown on those fixed shells premium eco cabins with my dog on a CDG-GIG flight, it was not pleasant at all to be frank, with the foot rest it was impossible to put the bag below the seat in front of us and it ended up being very very tight, fortunately our dog is very calm, sleeps the whole flight and does not complain. Here is a virtual tour of the cabin on 787 https://my.matterport.com/show/?m=HVWdQPyZ6Z6 so you can have an idea of the space.

We much preferred economy seats ( too bad AF does not have economy confort seats like KLM as those ones are perfect for travel with a dog given the extra space) , on AF we usually take a duo seat with my partner and the seats have in front of us have no separation on the floor and we can put the bag in between us. Also Too bad AF does not have a specific seat in J on which we could have our dog like some companies (AC, IB, LH, AZ....)