I do option 3. I wouldn’t consider option 4 particularly low cadence , but I do longer tempo efforts in the 30 minute range (at my more natural cadence range). I don’t do the other options.
At the moment I’m doing option 3 and I do it once a week. Presently I do it on a fairly flat section of road as it enables me to do it both ways. In fact that’s what I have scheduled today with 4 x 10 minutes with 5 mins recovery between. I do progressive overload with them and did 6 x 10 min last week.
I’ve found it’s helping improve performance. It’s another tool in the tool box.