I did a ton of upgrades from 3.1 to Windows 95 in late 1996 and early 1997 on 386 and 486 machines with 4MB of RAM. I still have a "mark" from the tedium. Some of the machines didn't have a large enough hard drive to store a copy of the setup files (the "CAB files") so until the company issued me a ZIP drive I had to do "the floppy shuffle" with 20-ish disks.

It ran like crap with 4MB of RAM but it did run. Opening anything much resulted in paging.

Your mileage may vary. I remember 4 MB booting, but being absolutely useless.

8 MB was still swapping all the time, you couldn't really run much beyond some simple software.

12 MB was finally enough to do something productive, but definitely nothing luxurious.