Such that the higher the resolution, the higher the clarity?
It can. But there are a number of other factors involved. When create the video, the encoding and settings have a factor as well. If you set a low bitrate, the video quality will decrease. Also, the encoding type, AVI vs. MPEG-1 vs. MPEG-4. Also if you upsample the resolution from say 720x480 to 1440x960, the clarity will suffer.
Also, "sampling" applies here.Example 1000, 2000 samples etc.The more filter samples you use the more clear it would look but mind you. Lot of memory would be worked on and also duration would be long; However you can also use less sampling and use clamp direct and indirect in order to filter fire flies easily. To achieve realistic result might take less time