Thanks for your interest in Pix4D software solutions.
We do not have any formal documentation on how to conduct terrestrial data collections just yet (but are working on it).
A spherical camera works well for interior mapping/modeling, but if used outside, often a large percentage of the area captured in each image is occupied by sky which doesn’t produce the best results.
Pix4Dmapper is hardware agnostic and can process images from virtually any digital camera. I’ve had good results with using my mobile phone (iPhone 7+) and have used standard GoPro Hero 3 cameras in addition to DJI OSMO and Sony A6000. When you are first starting, you may find it easier to capture video (ideally 4K which is comparable to 8.8mp image) as this will allow you some flexibility on how many frames to extract (4K video is often captured at 24 or 30 frames a second) and you can specify how often to sample a frame from you video file. You will want/need a higher overlap than the standard 70-75% range and more in the 85-90% overlap range. Scene lighting/illumination can be an issue as well and auxiliary lights may be needed to improve lighting across your scene. Every scene will produce different challenges and experimentation will help you understand what does and doesn’t work.