Hi @tyler4,
Welcome to the forums.
I am in a position to be able to provide some insights as I scoped out drop shipping/shopify/woocommerce at one point.
Will try to answer line by line.
We’re a small online business with a live and profitable website for travelers to book activities (i.e. they select # of people and dates from an activity calendar, each with their own inventory, and pay for it at checkout).
This sounds like a 2 sided marketplace with multiple vendors.
Definitely a use case that bubble fits in.
(we’re currently very lean with only 1 full-time software engineer / tech co-founder)
I would have been concerned if you didn’t have a technical co-founder. But with 1 full time techie, you’ll be totally fine if you end up using bubble.
The thinking is that leveraging off-the-shelf best practices for both frontend and backend ecommerce,
A wise move. If your use-case is something that falls within shopify’s scope, it is probably a better fit. The trouble happens when/if you step outside shopify’s scope. At that point, if you find a well maintained shopify app/plugin, then again, you could be fine.
However, customization is something that bubble will excel in far more. More on that later.
My initial impression is that it seems lite in the ecommerce department, doesn’t have many plug-ins (compared to like a WordPress, which has many mature ecommerce plugins)
From what I understand about your use-case, I think bubble.io has enough plugins to get you going quite far. Also, have you had a chance to look at templates? I think you may find some that provide a base for you to start on.
e.g. Zeroqode | No-code apps, plugins, native apps builder for bubble.io and more
Any insights into whether Bubble might be worth considering?
Without knowing more, its hard to tell. What I have noted is that established companies have a process. e.g. you already have a process in place and would like to take that online. Which is why you have a custom php site.
Now if you bend that business to fit shopify’s mould, you’ll be fine.
Or you could take bubble and easily flex it to fit your business.
There is also a trade-off between build vs buy. Initial investment vs ROI over time. Over time, you’ll definitely find bubble to be more flexible, extendable and adaptable. But the initial upfront to get started may take some investment.
I could go on and on about other aspects such as once you’ve gone through the bubble learning curve, you’ll get other ideas that you may wish to rapidly prototype and test various businesses which is what a lot of people do as well.
doesn’t have many Bubble-specific agencies either
There definitely are agencies that specialize in bubble. e.g. Zeroqode, airdev
But there is also another reason for that. Traditional development requires a large team that needs to combine many different skillsets e.g. architect, backend dev, dB person, devops, hosting, frontend, customer account manager etc etc. Using bubble, 1-2 person teams can go very very far and build pretty much the whole thing. Alongside pulling in a few people when needed. And there are many independents in that team size (including me btw!)
Bubble also seems marketed to startups, without engineers/programmers
For very straight forward use cases, founders can go quite far without engineers/programmers. Hence the marketing speak. However, the moment things get complicated, it is very easy to get into a tangled mess if people didn’t architect the app and lay down the right database architecture initially. There are definitely engineers/programmers here such as @zubairlk!
Bubble seems like it could be more customizable than a Shopify platform
Definitely Yes
and also possibly could be the next big innovative platform…? 
Definitely Yes. The overall zero/low code space is one to watch out for
Regards,
ZubairLK
p.s. I’ve also sent a PM.
