These could be checked from the tangible reports and impacts of NGOs accessible through their communication means and the vicinity of action.
I'll mention the example of The Shrewd Foundation, Ghana which is very active with Streetism. You can visit their website, go to the streets and communities to receive the positive feedbacks and negative ones as well which may inspire you.
You might also want to check, Spring Up Ghana with their library projects.
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You might question why I choose Ghana and not Cameroon.
Yes, because volunteering goes beyond borders. Equally, because they are relatable and volunteering is universal.
Also, no to mention the "big dons" so you don't get a bias view
Volunteerism gives the space for everyone to invest into their society, we might be volunteering for the same purpose, same niche but different results.