Not quite yet. HiDPI support is still unavailable in
stable versions of Reaper. And the 2x theme is not completely 2x, some elements are still
unscaled.
Also, the theme apparently won’t upscale correctly at higher-than-200% zooms like 300% or 400%. To address that, Reaper should be able to automatically proportionally scale currently selected theme according to arbitrary OS-level zoom, and preferably do this with no unreasonable blur at integer ratios — e.g. 200% theme should be blur-free at 400% since each image pixel can be represented as exactly 4 (2×2) OS-resolution pixels and blurry filtered interpolation is totally unneeded.
The overall HiDPI progress in Reaper is nice anyway though.