i just installed espimatic v0.26 on a 512kB esp01 with 64MB Spiffs.
it works! i gzipped all files like you did (with maximum compression) and uploaded them to the spiffs. even with the zipped files the esp reacts very fast. cannot see any difference to the common installation with non zipped files.
now having 92% space used andi can access the esp and it works without issues.
at the first boot i was able to access the isp directly with its ip adress. after i renamed the device in the setup, i now am only able to access the menu with http://IPadress/root.html
but that does not matter imo. installed a dht22, works as expected!
the disadvantage of the esp01 - you are only having 2 gpio