Hi, I have a Garmin 705 and there is no option to view intensity (IF) or TSS while riding. Does the Garmin edge 800 or 810 have this option to view while riding ???

The 810 does for sure, as does the 500 so I'd guess the 800 does as well. Just make sure your FTP is set appropriately and zero averaging is on.

705 displays power in Watts or percent FTP. What it doesn't have compared to the 500 is 3 second and 30 second power averages.