Hi Fido,
In HiFi terms I think of the razor as the Hi Fi itself, while the blades are the CD’s and the cream or soap is like the interconnecting leads, you do need all three to play anything but everything else is optional. In much the same way that a high end pair of speakers cannot make up for a poor source and gold plated interconnects can make a good sound even better, even the best skin conditioning products cannot make up for a blunt blade or bad lather but good balm can make a comfortable shave that little bit nicer. Given this I believe you need to take a balanced view and aim for decent products along with good technique across the whole shave.
I find some soaps are slightly more drying so I use a moisturiser when I use them. Some shaves a bit more raw for a number of reasons, I usually reach for the Dr Harris milk after those. I do not have a shave routine as such, although I do the same 2 pass with touch up and three pass shave with touch up at the weekend I adapt the products round the shave.
If I get up in the morning and am going to go eat first I will slap some Proraso pre/post on when I get up, if I am going to try a new blade I use a soap with high protection such as Tabac, when it is hot and humid outside I use different scents to the ones I use in the winter with the strong cold wind.
I guess if you are being really strict you do not need a brush, you do not need aftershave, moisturiser or alum, but they are nice to have. I chased the perfect shave routine for a long time working through nearly 40 types of blades, 25 different razors, 30 soaps and creams with a dozen brushes. Like you I took a methodical approach to systematically working through the permutations. I decided to start with blades so I bought an HD, a tub of good soap and an EJ brush keeping a spreadsheet to track how they faired compared of each other. I then tried razors followed by soaps and brushes.
I now realise there are probably more combinations than there are shaves, additionally some blades I scored highly are no longer available and some of the soaps have changed. On revisiting some of the products I thought were not so good I find that my improvement in technique changes my evaluation.
These days I do not keep such a precise track via a spreadsheet and now tend to work in group comparisons. About once a month I go to shave stash number two and pick out a few razors, some blades and about half a dozen soaps and creams. I take them to the bathroom cabinet and over the next few weeks I try different combinations paying attention to the good combinations that I am able to repeat to eliminate the flukes. The cream of the crop is noted and that gets carried over to next months selection. The ones I keep going back to I make sure I have stock of, and the ones I like only now and again I either PIF or do not replace when done. The ones I hate seem to sit there as I would not inflict them on anyone….anyone want a Wilkinson Sword soap bowl?....or perhaps some Dorco ST300s? or even better some other strange Indian made blades that will shave like a broken bottle?
The main point is that I do enjoy the pursuit of the perfect shaving combination and I realise it will probably never end. In the same way that I am nearly 38 and still attending education classes because I want to keep learning I know even when I have that perfect shave I will still look to see if I can better it.
Enjoy your journey, I do enjoy your reviews and thought provoking questions.