The biggest thing that will impact your work is connectivity. If the job is on Presto, and you are missing just one bar of reception, you will be SOL. Either it won't work at all and tell you you're offline or it will work very slowly which means taking forever uploading pictures as you stare at your screen and wait. This could be a real time waster. With all of the shops, submitting the data later at home is not forbidden. You can do it. The problem there is finding out too late that you either forgot to get a picture or got one that's too blurry and you'll already be home. As long as you get your work submitted within your deadline, doing the reports at home is not a problem, even though they make it seem like it is not an option. Just remember, that if the job is on Presto you must use the check in feature at the location. Or as close to it as possible in the case of no reception, adding a note in the comments as to why the check in address is not correct. I recommend allowing location tags on photos (hidden).
There are many discussions on these forums regarding various types of gas station shops. You may want to read about some other experiences which will give you an idea of what to expect.
Above all, just be aware that the company that now holds these contracts (from your description of the previous company I believe I know which) will always question your work, often gives incomplete instructions, and generally assumes that all shoppers are liars. So be extra careful, document everything and try to guess what the guidelines really mean. Sadly, the landscape in this regard has absolutely changed, and not for the better.