iPad feels too slippery to me as is. I get one of those screen protectors that give a paper-like feel to make it more like what I am used to from Remarkable.
Higher friction at the interface between tool and surface makes for easier control at the cost of requiring more force to produce a given result. That's why your hand and wrist get sore so quickly.
With a fountain pen or (presumably) an iPad with no screen protector, you have no choice but to learn to control the tool without that excess force - force which will eventually destroy a pen nib, and in both cases will ruin your lines because there's no friction to damp it. Learning not to overcontrol does take a little while, but pays off both in work that's neater and more skillful, and in being able to work much longer before aches force a pause.
(With the reMarkable, too, there's a benefit in that your stylus tips will last longer, and you'll get more nuance out of the pressure sensitivity with tools that make use of it.)
With a fountain pen or (presumably) an iPad with no screen protector, you have no choice but to learn to control the tool without that excess force - force which will eventually destroy a pen nib, and in both cases will ruin your lines because there's no friction to damp it. Learning not to overcontrol does take a little while, but pays off both in work that's neater and more skillful, and in being able to work much longer before aches force a pause.
(With the reMarkable, too, there's a benefit in that your stylus tips will last longer, and you'll get more nuance out of the pressure sensitivity with tools that make use of it.)