The next major release of Emacs is going to be awesome, because among other things the so-called PureGTK work was also merged, which means that it will support HiDPI screens properly on Wayland.
Do not use pgtk if you're not on Wayland. Its maintainer on the mailing list has been pretty adamant in stressing that the old gtk3 code is the better choice if you're on x11, while pgtk is targeting wayland (so they'd rather break x11 compatibility if it fixes a wayland bug)
That said, I've been running pgtk on GNOME Wayland on a hidpi screen and it's been great.