You need to get a PDOS certificate from POEA if the purpose of your resident visa is to convert it to an ARC and work here. Philippine immigration will check this, Taiwan immigration won’t. But just because Taiwan immigration won’t check it doesn’t mean it’s not important. You won’t be allowed to leave the Philippines, most likely, without a PDOS certificate.
You need an OEC if you are a returning worker to Taiwan. The Philippine immigration officers would check it. Taiwan immigration does not. Same thing as above.
Also, can you please do us legal Filipinos here a favor and try not to skirt the law because it’s inconvenient? If we were able to do it, so can you, SO SHOULD YOU.