Yes, they are sufficient for Quant, imo, as long as you have the ability to self-study. In particular, Bunuel’s Ultimate Quant Guide covers all the topics in the GMAT Focus Syllabus:
gmat-syllabus-for-focus-edition-424188.html.
And the two resources above are a bit on the advanced side. If you need to start from a more foundational level in Quant,
Manhattan Prep has a free book - GMAT Foundation of Math, downloadable from Amazon or their own website.
Imo, the real trade-off between paid course/book vs. free resources is between time and money. The paid courses/books are more "curated", so a bit more organized. With free resources, you’ll probably need to read a little more and do a bit more questions, but that in itself is not necessarily a bad thing.