Hi folks,
I writted a quite long post before deleting everything and write what you saw.
I expected the solution "just buy more ram or ssd" so here is my reasoning:
Both MacbookPro models, should work as fine as when first bought 7 years ago. It mustn't be natural to to make extra-investment if one doesn't get extra-benefits out of it. Instead save and save for a new model.
You should also understand that my country is not getting in a better economical stage, and therefore, expending requires a lot of prioritizing.
Secure vendors like OWC and Crucial requires expensive international shipping and income-taxes and importation fees to be paid in dollars for high-quality&expensive products. If alternate brands are known to be worst (like no working at all) then its quite like this MacBook will eventually die with its 4GB.
Catalina in both macbooks runs "just fine" but memory increases exponentially in 64bits.
At a bare install it takes 1.8GB, just opening safari with one tab for this post, leverages to 2.23GB. Of course there is memory caching and overall management involved handled by the kernel itself which eventually starts to do swapping in the spinning hard drive and makes everything worst.
In my measurements (in windows, because Catalina doesn't let met) 32bits appliances get 30 to 40% less memory usage than the exact same code compiled for 64bits, and 20 to 30% less Diskusage. I could also say that processor-performance is also reduced as there is less memory fragmentation, caching, addressing, etc. to be done by the OS, but it is really hard to measure.
So when Catalina forced to go for 64bits only and removed 32bits applications from the equation, the RAM-Usage by applications increased a lot just to do exactly the same tasks.
Also the new era of using node.js and electron to make multiplatform desktop applications which uses independly provided 64bits chromium cores (which gets duplicated on RAM) has became a major problem on memory consumption which for the soldered-RAM scenario won't go more than its 8GB, of course a fast SSD helps with the swapping.
Any way, as I say, I want to explore the alternative of using 32 bits applications in a 64 bits OS, like I do in my bootcamp.
Just to not waste unnecessarily huge amounts of RAM which is the most limited resource right now.
It may also be possible to disable macOS services just like one does in windows?
