As stocks of X10CJ depleted already..as it was previous series price to perfomance good contender..can also consider:
Sharp AHX9VED2 9700btu also a good contender for 1hp class, quiet ODU altho spec on ODU sound level NA

Samsung wise.. I think I scared most of my friends from getting one that I can't really comment on the ODU noise, the last one I dismantled was rather old series (so no comment)
Daikin ODU generally louder than average, spec on ODU sound level NA
Pana ODU 47db

However if you close the windows I think you won't really hear much noise from the ODU?

China haiiiiiiiii urgh one ODU confirm noisy as the ODU fan grille makes a metal on metal clattering noise lessen if u use hand to press it back firmly, will need modification to have rubber damper etc. Most other AC dont have this issue coz fan grille plastic made solve the metal on metal noise problem.
Usually multi split (aka System 3 4 5) common in SG and less common here.
It save cost upfront rather than buying many bigger 2hp units but if ur IDU is 1.0/1.5hp and you do not normally run all at once, but more towards 1 out of 3/4 total connected IDU the single split efficiency (power consumption) usually better than trying to get a 2.5L car to behave more like an axia fuel consumption in traffic jam..

It is used if u have very small place to put ODU; downside of having all eggs in 1 basket is that one ODU kaput all IDU also offline together.. generally in MY we dont face compressor space shortage unlike HDB in SG, many single split is recommended for redundancy.