I use surface book with 3000x2000 native resolution scaled 200%. I just reinstalled (spac)emacs with 25.1 version and a new emacs frame will start the right size then immediately halve in size as it starts to load and does not respect the 200% scale.
I have tried starting emacs on 100% then scaling up and all other such combinations to no success.
A partial solution exists:
(add-to-list 'default-frame-alist '(font . "Fira Code")) (set-face-attribute 'default t :font "Fira Code")
This will set the frame to a good level but has two issues:
dotspacemacs-default-fontoptions like bold, width.
Not everything is scaled back - in particular pylint code analysis popups are extremely small.
Once it is zoomed in it uses proper hdpi after setting
Disable display scaling on high DPI settings option on emacs.exe.