The fixed weight progression model is something I use mostly with beginners as well as people who are intimidated by adding more weight to the bar.
I’d say that it is the least effective progression model. Its main benefit is that there is a significant opportunity to focus on technique built-in by the use of the slow eccentrics and stato-dynamic reps.
The double progression works best with intermediate lifters or beginners with solid technique already. While it can work with advanced lifters, because the later already have a pretty high strength level, progression might be very slow with the double progression model, requiring you to stick with the method for several months.
I see the double progression model as the best progression model to use if someone doesn’t want to use a periodized training approach. The double progression model doesn’t work well with programs using blocks of training because each block is normally too short to properly take advantage of the double progression model. For example, if you have a 4-weeks accumulation block, a 4-weeks intensification block and a 4-weeks realization block, you would need to switch your training zone/number of reps, every 4 weeks. And 4 weeks is typically not long enough to get the most out of the double progression model.
That’s why it’s best used if someone plans to stick to a similar training zone for 6-12 weeks.
Percentage-based progression is something I typically use only with advanced lifters or with those who need to peak their strength at a specific date. The problem with % based progression and beginners is that it’s a lot harder to predict their weekly progression and use percentages that make sense. You also need solid technique and a consistent performance level for it to work. A beginner will have a lot more fluctuation in their strength-performance capacity (because of they are less efficient, have less stable technique, a technique that changes with heavy weights and poorer recovery) and it’s much easier to be off target with the progression.
For example, I used a percent-based progression model with someone fairly new to strength work. And at one point he had to do max reps at 95% of his pre-cycle 1RM. I was expecting 5 ish reps and he did 13… he progressed much faster than I planned, and he left gains on the table because of it. But the opposite can happen.
You are correct about the ramp-up.
During accumulation phases I normally prefer to progress by adding reps with the same weight (which theoretically qualifies as a form of fixed weight progression) or adding sets, although in both cases I do tell the client to add weight if he feels that he can, but it’s not the main progression.
If I’m using the omni-contraction system, on eccentric day, during the accumulation phase I typically shoot to increase the duration of the eccentric phase while keeping the same reps and at least keeping the same weight. Same thing for the stato-dynamic day in which he either add holds (e.g. from 1 to 2 to 3 per rep) and/or the duration of the holds.
On the intensification phase of the omni-contraction I like to do the opposite: decrease the duration of the eccentric phase or the number/duration of the holds while singificantly adding weight.