Change David502 firmware to openwrt 19.07.5

Which firmware image should I try to use to change from David502 firmware below?

Will the openwrt 19.07.5 sysupgrade work OK? Is there anything else I need to know before upgrading?]

Use the one with sysupgrade in the name to change from one OpenWrt version (including third party builds) to another.

When making a major change it is best not to save settings, reconfigure the new install from scratch. If you have a complex configuration you can export the settings tar file to be an archive which you can refer to (configurations are in text files).