TBH, it's all much of a muchness, really. Every RGB system has its upsides... and its issues with software conflicts. Every one of them will have forum posts full of screaming kids whining that they bricked something because they mixed incompatible kit, or somesuch. The best RGB solution is a standalone one that does not use USB addressing and is not reliant on
all your RGB kit being from Asus, or MSI, or Gigabyte, or any of that.
However... Corsair's iCUE system is pretty decent and while it's not always amazing (the others aren't amazing either), it's also far 'less bad' than all the others. I generally find there are fewer complaints and fewer critical issues when using Corsair's system compared to mobo manufacturers' own ones. ALso, while you'll have to keep within the Corsair iCUE ecosystem, it
is a whole ecosystem and there are plenty of RGB things you can add to the build... including their own HydroX series.
The two main issues you'll have with RGB are:
1/. 16 million colours, combinations and patterns. Do NOT limit yourself to the "flashing unicorn rainbow puke" demo mode that all the sellers use. This one is why so many people hate 'everything' about* RGB!
2/. You're generally limited to lit fans, light strips and a few components that have either random LEDs and/or garish logos... unless you get something custom-built.
Additionally, if using standalones:
3/. Standalone systems will likely not control any of the motherboard or RAM LEDs. You'll have to use the dedicated manufacturer(s) software for that, and that's often where you get troublesome conflicts.
4/. Standalone systems like those from Corsair and Phanteks frequently use proprietary connectors, so will not play well with others. Some have adaptors, but then see 3/. above.
I wish I could help further, but for the past couple of years I've been watching from the wings and debating which system, if any, is good enough to get for my own rig.