For trigo, it helps a lot. Especially as a lot of formulae are their. It helps to get a good grip.
Also, not many questions are now asked directly on trigo.
Better, do Rd then, go for Amit aggrawal.
If you feel well versed with formulae, then anytime you can skip RD.
Rd won't increase the level of thinking capacity much. So, do accordingly.
It is exhaustive, so do only the portions you feel you need practice.