@Otmar K Just found the culprit for the strange stops on moving in front of the camera. If I set the control strip/touch bar to show just the function keys the issue is gone. Not sure if this is a bug in the Xojo-framework though..
Considering the Xojo framework sits atop the various Apple frameworks, I would be inclined to think that this is an Apple issue, where it's probably (although I have no evidence) polling the application demanding it update it's touchbar elements, that it doesn't have. The Touchbar is buggy and has caused many issues for developers.
@Otmar K Moving the drawing direct to the canvas has solved the speed issue for the MBP2018, but there's still this factor 3 slowness of the new computer, and this weird reacting to movements in front of the camera.
Glad to hear it helped, that 3x slowdown really does sound like an issue with the machine to me. If your previous MacBook was non-retina, it would make sense, but earlier on you stated it was retina, and with older hardware it *shouldn't* be faster. My guess is either a bad driver or that integrated graphics chip on the 2018 is really designed to either fit in a smaller chassis or to use as less power as before (so Apple can claim 10 hours on a physically smaller battery).
I would look into finding something that can benchmark the GPU.
@Jeff T I just had the exact same experience. The other main reason I sent it back was I couldn't use any peripherals with it.. 4 USB-C ports are fine if the rest of the world uses USB-C, but having to buy an adaptor to make any standard device work.. that's crazy.
Overnight I lost access to my printer, external HD, CD drive, camera...
I had ordered a bunch of adapters to go with the machine, I would have appreciated it it still included at least one USB-A and a SD Card slot (all 4 of my cameras use SD cards). Ultimately it came down to the fact that it wasn't a machine I wanted to own, it's performance was underwhelming for a 5 year newer model, the keyboard is unreliable (every key still works on my 2012, but my 2015 is now getting ready for it's 3rd keyboard), the ports were inconvenient, the TouchBar is a joke, the battery life is a huge disappointment (it got the same battery life as my 2012, which needs a new battery), and at that time, it still didn't have enough RAM. Apple increased the price and at the same time obliterated the value of the machine, I just didn't feel it was worth $4,000. So I'm sticking with my 2012 until either it completely dies, or Apple actually wise-up and make a MacBook Pro.