LOL @ shipping - I live in the third world and am still waiting on stuff I ordered in October :)
The TinyG is modular, in that you can plug in external drivers and slave two (or more) TinyG together to give as many axis/control points as you need (for assembly, pick and place, etc.).
But, it looks like 32/64 bit is the way forward and the TinyG is going to run out of puff in the future. Still, it's a cheap enough board that it can always be put to use in another project later on...
I have a number of controllers, including TinyG, Marlin on the same Xmega board as the Tiny, Smoothieboard, GRBL, and I reach for the TinyG more times than not.
I've got a 4-axis and 5-axis Smoothieboard I haven't even used, despite it's connectivity and axis advantages - the motor drivers are the same as your GRBL shield, and I'm not ready to buy some Longshine-type drivers yet. The Tiny works well with my Ox-style Openbuilds machine using belt drive. Maybe if I move to leadscrew I will want more power, but I mostly carve and cut acrylic and ply, so I don't need a whole heap of power.
I did note that the development seems to have tailed off on the G2, for whatever reason, and that's why I haven't bothered doing anything with it.
The last commit on git was over a month ago and the one before was six weeks before that, then a month before - not a bleeding-edge active project, by the looks.
If I was being asked... I would look at one of the Smoothie boards - there's a tonne of them out there that offer all sorts of options.
MKS, the maker of hundreds of thousands of Marlin boards has one that's pretty attractive at Euro 45 for 5 axis using the DRV8825 driver (a step above the DRV8818 in the Tiny). https://www.aliexpress.com/item/MKS-SBASE-V1-3-S-32bit-Armplatform-Smooth-control-board-open-source-MCU-LPC1768-support-Ethernet/32823546897.html
It will be my next controller, I think.