@erictgrubaugh's youtube channel is great for beginners:
https://www.youtube.com/c/StoicSoftware/videos
But the NS help docs are beneficial as well - governance is listed for all functions.
Like you mentioned, creating a search is more efficient than loading a record... though using search.lookup is generally even more efficient than creating and running a search.
But knowing when to use which is something that come with experience.
I'd also recommend looking over sample code like
@dansteg mentioned.
I learn best when given a working example, then changing certain things to see how that impacts the results.
A ton of samples can be found in the help docs here:
https://system.netsuite.com/app/help/helpcenter.nl?fid=chapter_1551381633.html