I would suggest https://www.connectedpapers.com/ for finding the most appropriate references on a given topic. I recently discovered this and it's free.
Prof. Qamar Ul Islam has provided a list of candidate tools. Zotero is free and open-source. In Mendeley (free but not open-source) I appreciate highly a feature allowing quick and accurate importing of any doi: Copy the doi address and paste it into the corresponding field in the manual addition window. Then, clicking on the magnifying glass / lookup button retrieves automatically all article's information.
Regarding team collaboration, we have conducted several systematic reviews on topics such as e-learning, virtual reality, augmented reality, game-based learning, human-computer interaction etc. We have found using collaborative platforms such as Google Drive an effective solution for document sharing, note taking and coding of articles.
I would also recommend LaTeX (and BibTeX accordingly). Even though it is not a user friendly "framework" (especially for text intensive manuscripts), it is very powerful in exporting the references correctly for the reference styles of different journals. However, if you have a math-expression intensive manuscript, LaTeX-BibTeX is probably the most efficient way to write the manuscript and revise it to different templates of different journals.
JabRef is excelent for managing bibliographies and PDFs (jabref.org or www.fosshub.com/JabRef.html). It uses LaTeX BibTex format, can grab details from a DOI, and even find full-text PDFs sometimes. There is a browser plugin for automatic reference generation, and the database can be seen on Android with the Library app.
There have been several good suggestions made by previous replies.
I would focus on the question from practical applications point of view - free tools for extensive systematic review. For this purposes free reference managers are Mendelay and Zotero. Depending on wether You need to exchange the original article files with colleagues, Zotero is applicable in exchanging the full text outside the journal databases.
Free tool for manuscript screening is Colandr - https://www.colandrapp.com/
Free tool for searching with batch downloading and analysis from Google Scholar is - Publish or Perish - https://harzing.com/resources/publish-or-perish
Reference management as well as academic mapping/heat mapping tools were already proposed previously.
Review software like colandr as proposed by Ahto Kangur is another type of software and facilitates already the review process and cooperation with the co-authors (even internationally). I myself am using colandr at the moment and find it quiet helpful for the process.
an overview of such software, with feature description can be found in this article:
Article Software tools to support title and abstract screening for s...
another good place to look for specific tools for automation some of the steps in a review process is the SR tool box, see reference + link below:
Marshall, C., Sutton, A., O'Keefe, H., Johnson, E. (Eds.). (2021). The Systematic Review Toolbox. Available from: http://www.systematicreviewtools.com/
I have just been trying to keep references from papers in a huge bibliography I put together in an MS Word document. Do you think that it's better to use tool like EndNote?
I used Mendeley. In this software, classification and maintaining the literature is easy. It is also easy for reading and citing the literatures through Mendeley.
I will go a bit a different route though these other tools are super helpful as well. There is a Machine Learning assisted program called ASReview which is really good for systematic literature reviews, where it can use machine learning to capture the most relevant papers in a large stack of literature. The output is then nicely formatted where you can review your selected relevant papers and review from there and you can build your review document from this output. Hope this helps and happy reviewing!