I have two pcf8575 modules.
https://www.ebay.com/itm/PCF8575-I2C-IO ... SwBPxcb6Qq
The first is this and everything works perfectly.
https://www.ebay.com/itm/PCF8575-16-bit ... Swqlha-Pgs
This is the second but even if it is correctly identified (0x20) it can not make the relays work. The leds are barely visible when turned on. The wiring is like the one you indicated with 10k resistances between sda/5v and scl/5v.
I would like to use the latter pcf8575 because I have already printed the board