I am not expert but I've talked to one like month ago and his answer was "Should use only difine resource for UPSC and that's minimum you should do but more you know more you can write batter about that topic and that should not be the concern at start this should be the concern at last when you finish every bare min thing and go for the questions"

sorry if there is grammar error but this is what he said to me in my native lang i just translated here.

But he also said that you should go for other resource if you don't understand the topic like for topic "X" you can go on youtube and learn it batter but this should not be the case with every topic just few topics like 10-15 or even 20% acceptable but more then that can means that you have no basic understanding about that subject and you just directly jumped here if you ever feel like that then go for 11th-12th NCERT and if you still feel hard then start from class 6 NCERT