I lean towards your first and last attempts, at least in general design direction. You’ve got some room to improve on the execution in general, but I’ll explain why I like those two the best.
The first is very simple, minimalistic, and hits all of the goals you listed for aesthetic communication. It’s very efficient in that way - it doesn’t take a lot of fluff to tell you what’s going on, and it’s not saying anything other than what it’s there to say. I look at it and I hear “Clean” first, and that’s a solid starting point.
The fourth I like for a similar reason, in that it illustrates what it’s trying to convey clearly - but in this case directly with illustrations, rather than design language - but also in that it’s fun and visually interesting concept. The style is still fairly modern and simplistic, but the content itself gives you something to look at. With the audience you’ve listed, I think it’s simple enough to not over-stimulate and confuse a target, but interesting enough that they’ll remember it.
The other two, I think, have too much going on, on different fronts. The gradients on number two, while nice, kind of muddy the colors, which I think interferes with your message of cleanliness. I do like the waves, and the subsequent evocation of cleanliness through that, but I think the shape motion and color motion are too much, together. My take on the third is kind of the inverse, in that I like the cleanliness of the colors and overall simplicity, but I’m not as sold on the shape language. It’s hard to say how much of my unease is getting stuck on the seams on your line joins (I can see the rounded edges where the strokes meet, and that’s bothering me) or the unbalanced motion on the front, or something else that I can’t quite articulate. In summary, on #2 I’d pull back a little, and on #3 I’d go a little harder.
To put it another way, I think I like #1 because it’s the simplest, and I like number 4 because it’s the most interesting and approachable to a layman, while #2 & #3, while interesting, I think are more complicated than they need to be to do their job, and less clear than they could be in what they’re trying to say. Rephrasing again, I think I’d summarize 1 as Simple/Abstract, #2 & #3 as Busy/Abstract, and #4 as Busy/Direct. I think they’re all decent concepts, but if I were weeding them out, I’d drop or rework the two in the middle first. I hope that this helps, I notice there’s a lot of mixed opinions here.