They've all been variants on an ESP32 microcontroller, some kind of 3.3v power supply then a load of headers for the specific peripherals I want for that specific project.
My SMD soldering is a bit hit and miss, I've had a few irritating failures from creating shorts under big modules like the ESP32-WROOM or the uSD socket. I'm OK at putting solder paste on, but then I tend to very slightly botch the placement and have to nudge the module into place smearing it. I just don't have hands steady enough to get it right first time. I'm fine with the smaller components.
On the whole though it's a positive experience and I've got better at this than when I was first ordering things in 2019.
One of the things that changed since then is the proliferation of microcontrollers that have native USB support. Now there are multiple ESP32 variants with it but it's appearing all over the place, right down to the ultra-cheap RISC-V chips from WCH.
The boards above have ESP32-S2 modules but I'm also making things with the ESP32-C3, which I'm coming to really like due to low cost, native USB for programming and just enough GPIO for most things.
The upshot of this is making boards with USB naturally leads to wanting USB connectors for the boards.
Which I dislike.
Low volume electronics projects with SMD soldered micro-USB sockets have a bad history for me. I've damaged or totally ripped off the socket on more than one board and they're often just a bit cruddy. Professionally made high volume products are better but it's still a weak point.
The obvious solution is to fit USB-C, which addresses many of the issues but have you looked at the soldering footprint for one? Nope. Also I don't need USB-C. These are USB 1.1 devices with no need for Power Delivery or anything smart.
So I've embraced old-school full size USB-B connectors for the larger PCBs. They're trivial to hand solder and robust. Which is good if they're likely to get rough handling, which some of these may do. If it's going in a physically large object the extra size isn't going to matter.
The ESP32-C3 is replacing the ESP8266 in my affections and I ordered twenty of this PCB. It is effectively a small battery efficient development board. So I've reinvented the wheel a bit.
In the kind of projects where I expect to use this I often bury the main PCB inside somewhere but will want the USB socket accessible in the side of the enclosure.
Having the USB socket on a short flying lead is convenient for this and USB is more tolerant of this than you'd expect. In principle you need to match the track impedances/lengths etc. but in practice you get way with it. It adds a lot of flexibility and if the socket gets damaged it can be easily replaced.
Separating the the USB socket also means I can come up with whatever power path I want at time of build. Some things are going to have LiPo batteries and want an onboard charger. Some will have removable batteries. Some will be USB powered. These boards are generic after all.
I may come back to this and design myself a board that includes onboard power path management/charging for a single LiPo cell, which I did on an old design, but for now I'm happy with how these are coming out.
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