I am starting a 2e Planescape mini campaign with all new (to 2e) players (and myself a new-to-2e DM). I am going to start with The Eternal Boundary first but wasn't sure if it was doable for a level 1 party. Should I have them start at level 2 instead? Is there a recommended level by the time they get to the Citadel of Fire?

Also, would level 2 be harder to learn and play than level 1? My 5e brain's instinct is "there's more to learn at level 2 than level 1" but actually looking at the 2e classes that doesn't seem to be the case. I'd like to get to level 5 at least in 7-8 sessions of this campaign - could I start them at level 3 or would that be too much for all beginners?