I like to get in front of my subjects “en plein air” if I can. Even in my allotment pictures (which are partly from imagination) the core elements are taken from real allotments. Working on site you get so much more from what you are trying to capture, I also get to chat to passersby who feed into my work with their rich stories and conversation. For me working purely in the studio would be like painting through a letter box.
In regards to perspective, the early part of my career was drawing and airbrushing full 3D cutaways of fighters and ships for the MoD so I know a fair bit about getting perspective right if I need to.
Accurate perspective however is all well and good, although in creative terms it can only deliver so much. I tend to adjust and push things about until it feels right. If that means geometric perspective is abandoned then that’s fine. It’s all about the overall impression.