I had used a RX 480 4Gb for quite a while and 4K60p youtube could not run without dropping frames. 24p & 30p could work if I OC:ed a little but it was dependent on the material if it would run trouble free.
Was only as of late with new updates to software it seemed to work in the last few months.
A RX 550 I can't see be issue free for you goal unless you get the Video decoding to work 100% issue free, but if decoding works any card should work, even APU/integrated graphics.
Hardware acceleration works and breaks at times with drivers or software updates and a RX 550 doesn't have the muscle to brute-force I would guess when the acceleration hardware isn't working.
Netflix support has specific requirement of supported hardware, make sure you have those. Decoding requirements of supported features to accelerate.
Gigabyte X570 AORUS XTREME, Ryzen 7 3800X 4.4Ghz, 4266/1900 MEM/FCLK, 188.8.131.52.76.tRFC 650 1T 1.600V
4x8Gb Kingston HX434C19FB2K2/16 3466C19 1.2V (Micron E-die 16nm)
OLD: Biostar x470GT8 Ryzen 7 1700 @ ~4.0Ghz CPU, 3200Mhz RAM ...