What do you want out of your time?

Immediate lives saved? Impact on the distant future? Building new skills? Widening your professional network? Having a good time?

Once you know what you want, and which of the above you consider to be "effective" uses of your time, you'll have a better answer to your question.

More in the same vein in this article: https://forum.effectivealtruism.org/posts/ScLHyCY6JCr5FtuiY/effective-volunteering

Making money from Twitch or blogging is very difficult. I think you'll enjoy the process of blogging/streaming a lot more if you aren't doing it with revenue in mind, at least until you reach a reasonable following.

For perspective: Twitch streamers make ~$3.50/month/subscriber. If your job pays, say, $50/hour, you'd need 100 Twitch subscribers (which I'd guess would take months to accomplish even if your stream is polished and highly watchable from the beginning) to pull in revenue equivalent to working seven more hours each month. 

(Of course, you may not be able to "add hours" in that fashion, but I still find the comparison helpful -- and you may be able to do some freelance consulting or something like that.)

This seems like a classic case of it being okay to have more than one goal. Your hobbies can be hobbies without having to be impactful; your work, if it is your primary source of impact, seems like a better place to focus if you want to boost that impact.

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All that aside, if you do build a strong following on a blog or stream, that can be a good opportunity to advertise effective giving, and it probably won't hurt donations if you mention that they go toward really good charities.* I've considered doing this if I ever open my own Twitch stream up for donations.

*...although, come to think of it, many people probably donate to streamers/bloggers in order to support their work/the cool person behind it. So perhaps the charity angle would hurt more than it helped?

I would think hard about what the relevant resources are that you're trading off against each other. Are your hobbies important for your well-being and relaxation? Is it possible that by starting to monetize your hobbies, you might get less enjoyment out of them? Maybe it will also create some imbalance as you spend more time on them than you otherwise would? Or perhaps it's the opposite and monetizing your hobbies would actually increase the quality of your leisure time? Perhaps you can run a time-limited experiment to find out.

Also, as a full-time online entrepreneur my opinion is that neither blogging nor streaming are particularly good income streams unless you have reason to think you would be exceptionally good in either of these.

Also, have you read this? https://www.lesswrong.com/posts/3p3CYauiX8oLjmwRF/purchase-fuzzies-and-utilons-separately