I went to a watch fair this fall and got to see offerings from Halios, Oak and Oscar, Autodromo, etc.
As with any watch, it helps to handle before buying. Since most of these watches have generic movements, a good chunk of the quality (or lack thereof) can be seen and felt in the finishing and details. But when you can't see the watches in person, I think the second best factor is to trust the humans behind the brand. Look for interviews with founders and watch reviews. If you buy the story, you'll buy the watch.
The best part of seeing the micros in a watch fair setting is getting to meet the folks (or one-man show) behind the brands. There's nothing quite like putting a face to a name and getting the sense of accountability they have for their product design, QC, and service (and even answering their own emails!). If they nail that, then they earn my respect as a consumer.
There are interviews with Dan Henry and Oak & Oscar on the Worn and Wound Podcast that illustrate this well. They both discuss their level of personal involvement with design and manufacturing quality control.
That said--I wouldn't mind a Halios Seaforth and an Autodromo Group B!