Increasing duration and decreasing % FTP or the oposite?
For example doing a few workouts (weeks) 5x5 at 105ish% and after that 4x4 at 110ish% and after few pf them 5x3 at 120ish%…
I found that some suggests this approach and some the oposite?
What you guys found better?
How you approach this depends on what your training for…repeatability, capacity, power etc. This would massively influence how you string the sessions together.
Try Short intense period before starting base? Chad's short FTP boost plan - #4 by Supermurph19 for some discussion on this.
Or just browse through the progression levels for VO2Max workouts.
TBH those are probably too easy… 5 x 5 should be a walk in the park. A real 5 x 5 closer to 120% and you might not finish the set if you are relatively new to training. So maybe do the 5 x 3 at 120% as you mentioned, then go for 6 x 3 if you can.
The wko suggestion from Tim Cusick is below, but rather than just GO HARDER, consider Hard starts…ie: 30s at 120-130%, then just 4m30s at 110%…you’ll get a redonk vo2 response from that most likely, and prob easier to finish unless that hard start really breaks you (hard to say here, I don’t know you!) But low FRC rider might have a tougher time with those than high FRC rider who can bam bam all day…
good luck!
A very broad answer would be: whatever gets you to stay at the 90+% of your HRmax for as long as possible.
If you struggle with holding high power for long time, do shorter intervals; if you need longer time for your muscles to fatigue and your HR to rise, do longer intervals.
The end goal is the same: accumulating time at high HR values.
EDIT: I realised I didn’t actually answer the question. Tim Cusick’s approach is going harder (more power) for a certain duration (picture @Dschlag posted above). I remember listening to some other podcasts on the topic and the main focus was on what I said above. I guess the answer is similar to most answers: there’s more than one way to skin a cat.
Forget about %FTP.
The key is in the zone: VO2 MAX.
Pick a duration you can complete going REALLY, REALLY hard. Add more rest between intervals if necessary to complete.
Have fun! 
