isang is often used after the SA prepositional marker rather than repeat NG
NA is an ADJECTIVE MARKER/CONNECTER/LIGATURE before or after a COMMON NOUN ( any noun other than pronouns or proper names). The adjective is TIED to the noun so rather than "dangle" the adjective is super clear what noun is modified.
ANG adjective NA focus noun (or post-position ANG focus noun NA adjective)
NG adjective NA non-focus noun (or post-position NG non-focus noun NA adjective)
And of course...NA switches to -ng for adjectives ending in a vowel or -g for adjectives ending in N.
And could be more details...depende depende...palagi...
To my ear...Filipino is classic Tertris...Jurassic naman! Few ideas clarrified and smoothed to the ear by connectors throughout. Just connect all the parts if you can hang...