Speaking to the save file part - it just has game data. Variables/etc. I junction the save folder that renpy uses in the appdata\ location to a shared network drive, and then have multiple systems that use it. So between various systems of various specs, they dont care. Just needs to be junction-ed on each machine to the network path. This way beyond the local copy each game has, the network copy is kept up-to-date across machines.
As for sys specs.. it does seem the later 7x versions of renpy, and potentially the newer 8x does not like older cpu/gpu hardware, and especially certain igpu/apu setups. Just seen too many posts from various people with very low, or old spec machines having issues with renpy games. While renpy is not that heavy of an engine, and it doesnt have high overhead, I think it just comes down to the python code processing and how it interacts with certain drivers/firmware.