Raid strength depends on a lot of factors. Formula you can find here:
https://rimworldwiki.com/wiki/Raider
You can alter some parameters via some mods. Example:
https://steamcommunity.com/sharedfiles/filedetails/?id=1722803450
If you want wealth to be disabled - and time being mostly the difficulty factor:
https://steamcommunity.com/sharedfiles/filedetails/?id=1624131230
https://rimworldwiki.com/wiki/Raider
You can alter some parameters via some mods. Example:
https://steamcommunity.com/sharedfiles/filedetails/?id=1722803450
If you want wealth to be disabled - and time being mostly the difficulty factor:
https://steamcommunity.com/sharedfiles/filedetails/?id=1624131230