If the 3D monitor you're going to buy support displaying 3D images by receiving a "side by side" picture, then you can use TriDef 3D with latest development builds just fine (as far as you use Direct3D 11 - TriDef 3D isn't fully compatible with OpenGL yet).
TriDef 3D is also able to directly send 3D signals through an HDMI cable to a compatible TV/monitor like nVidia 3D Vision, but it works with any GPU, not only nVidia ones, however this mode doesn't work with DX11/OGL because current Dolphin builds still lacks the exclusive full screen mode that DX9 implemented in a veeeeery buggy way (when you enabled 3D Vision in DX9)...
TriDef 3D is also able to directly send 3D signals through an HDMI cable to a compatible TV/monitor like nVidia 3D Vision, but it works with any GPU, not only nVidia ones, however this mode doesn't work with DX11/OGL because current Dolphin builds still lacks the exclusive full screen mode that DX9 implemented in a veeeeery buggy way (when you enabled 3D Vision in DX9)...
Avell A70 MOB: Core i7-11800H, GeForce RTX 3060, 16 GB DDR4-3200, Windows 11 (Insider Preview)
ASRock Z97M OC Formula: Pentium G3258, GeForce GT 440, 16 GB DDR3-1600, Windows 10 (22H2)
ASRock Z97M OC Formula: Pentium G3258, GeForce GT 440, 16 GB DDR3-1600, Windows 10 (22H2)