It depends on the system, but in most cases I think that larger timeframes bring larger profits. First of all it is a historical fact, probably came from the stock market, things can change in the years to come, due to growing popularity of day trading. Market changes with the people, and people more and more like daytrading.
Second, there is a law, the lower your risks are, the lower your profits are. It you have a system using the same ratios ( rations, not exact figures) for SL and TP then the ammount of capital you risk on smaller timeframes is smaller the the one you risk on a large timeframe, ergo the profits are smaller.
Having more positions could make your system more profitable, again, it depends on the system. For example one system could generate 2+3+1 for a week on a small timeframe chart, and in the same time it could generate 10 for the same time on a daily chart.
So once again, depends on the system, and there is no rule expept this one.