わたしは or わたしが?? は(wa) vs が(ga): the difference between は and が Japanese subject particle/topic marker

Topic / Subject particle in Japanese wa and ga

は (wa) or が (ga)? Which should I use the subject particle in Japanese sentence??

In Japanese, subject particles are not that simple. Yes, you can say it depends on the context but actually not always.

You can review basics in the following pages:

Topic Particle は

https://www.hanaskyglobal.com/topic-particle-%E3%81%AF

Subject Particle が

https://www.hanaskyglobal.com/subject-particle-%E3%81%8C

References:

Wikipedia 'Topic marker'

Wikipedia 'Topic and comment'

アルク　ことばの仕組み（文法）

東京大学　日本語センター　助詞「は」と〈情報構造〉