exec xrandr --dpi 192

Scripting ~/.Xresources is not possible (AFAIK) but you could use xrdb to load specific configuration files from (eg) ~/.xsessionrc.

I'm on a fresh Devuan install and I intend to start using I3 on a regular basis, but I still want to keep xfce for various reasons.
My screen is 3200x1800 on 13 inches, so it is just fine on xfce with the scaling parameter (x2).
On I3, I found the solution to add

Xft.dpi: 192

to the .Xresources file, but it also changes it in xfce and screws it up...

I'm not familiar with languages and scripts but I wondered if it would be possible, in .Xresources, to put as a condition for the xft parameter to detect if i3 is running, then apply, or if xfce s not running then apply.
Also I thought about customizing the ~/.config/i3/config file with a similar parameter but I'm not sure it's possible. My attempt for now (adding

Xft.dpi: 192

at the end of this file) simply led to an error message in i3.

Thank you for reading ! I'll leave it a little and try again later.

best regards
PierreP