Like you, I don't have much experience yet on Medium, so I'm still learning what works for me. That said, I don't think there is any one 'right' way to go about things. I see a lot of top writers producing high volume fluff, and others who write more considered and thorough work.
So far, when I publish every day, I get steady trickle of new followers. When I take time off, the increase definitely slows. At the same time, writing for quantity definitely compromises quality. It's really a difficult balancing act and I'm still trying to figure it out.
The publication you mentioned at the end of your comment is my publisher of last resort. I submit there when I've already been rejected several times elsewhere. They publish 50-100 stories a day, so your work gets buried instantly there. Also, the publication owner has hundreds of his own stories to scroll through at the top of the publication's homepage, so the 'latest' stories are buried in that way, also. Finally, I've only been selected for further distribution once in that publication, whereas I'm almost always selected everywhere else. Some writers swear by that publication, but to me, you'd be better off trying other options first.
I try to manage the quantity/quality balance by writing something light for daily publication while working on more intense projects to submit to non-Medium literary publications. I recently had a short story accepted by a small indie publisher after a few weeks worth of work. I've also got a personal essay in the works that I will be submitting to large magazines before shopping it anywhere on Medium.
Books Are Our Super Power is really my home on Medium. I have an MA in English and therefore have a vast store of material to draw on when I write book reviews. That enables me to maximize both quality and quantity, which creates the highest value for both me and my readers. Plus, Books Are Our Super Power has high editorial standards, so it is a prestige publication. I'm a 'Top Writer' in both 'books' and 'reading' in large part because of my relationship with Books Are Our Super Power.
Since your background is in science, perhaps that should be your go-to topic? And perhaps scientific publications should be your 'home' on Medium?
I also think rejection is a good thing. If I submit something substandard and it gets published anyway because of low editorial standards, that actually hurts my brand. In the long run, I'd rather my low-quality work get rejected than go public. I only keep shopping an article after rejection when I truly believe in it. I have made a few missteps in that regard--I have 'anxiety submitted' a couple of articles to that easier publication you mentioned that I'd like to get back now. I published with them recently only because I couldn't find a good fit for that article elsewhere. It got selected for further distribution, which confirms to me that it was a quality story, just not right for the other publications I tried first.
That's a long way of saying that you should set your bar high. I love that you're going to pitch Better Humans and that you've already submitted to Mind Cafe. If you get rejected, try those articles elsewhere and keeping pitching new ones, too!
You should also try The Ascent and The Writing Cooperative. They are large publications that publish quality stories and are open to new writers. You can expect to be rejected by them sometimes, but I think you're also certain to be accepted sometimes, too. You write good stuff, so those publications will want your work!