I can only tell you what did or didn't work for my printer.
I have some high quality 0.9 degree NEMA17 motors left over from a past project.
They have winding resistances and currents that are surprisingly similar to the ones that FT supplies.
Their torque curves are different though (see below).
So I tried one on the original FT-5 non-geared extruder first.
Couldn't get anywhere near enough torque out of it.
So I scrapped my thought to try them on the X, Y or Z axes and made other plans.
I changed to a geared (E3D Titan) extruder instead which has approximately a 3:1 reduction ratio (it doesn't equate to the exact gear ratio because of a difference in the extruder gear diameter).
Tons of torque, no real problems. Very happy.
Then I changed the driven Z pulleys (on the leadscrews) to 40 tooth versions.
Now it has a 2:1 reduction ratio with the stock motors and motor pulleys.
Worked like a charm and I now routinely print with 0.1mm layer heights (and I have tried smaller ones).
I simply couldn't do that before.
In general you won't get as much torque from a given 0.9 degree motor as from its 1.8 degree counterpart, all other things being equal.
Unless you spend a ton of money on super precision (ultra small rotor to stator gap) versions.
They will run out of torque at lower stepping speeds, and probably don't have as much to start with.
A Titan (or similar) setup and a pair of 40 tooth pulleys is a whole lot less expensive.
Quite a few of the "hackaday" articles are interesting.
But you have to ask yourself who wrote them, if they actually tested what was in it, and in this case was it written for a smaller (lighter weight component) printer setup?
Were they running the resulting printer slower, assuming it was even built?
Your experiences may vary.
There definitely are people who run 0.9 degree motors on FT-5's.
My particular motors just weren't remotely powerful enough at the same driver currents (or even higher).
Am I willing to invest in different ones as a test? No.
I am very pleased with the setup I have at the moment.