Would this work with that powered 4x-16x riser?
Which powered riser specifically?
This one: https://smallformfactor.net/forum/threads/thin-mini-itx-powered-pcie-riser-4x-to-16x.5852/
I believe it's too tall.
Maybe not. It's about 40mm high which gives enough room for it to fit inside. Problem is, you just can't connect a GPU directly to the x16 slot unless you use an offset CPU cooler with thin heatpipes as shown there.
To use it in this particular case, you'd have to offset the GPU instead, with a 5cm riser cable, so that it can be placed in the single low profile slot.
I'm running the same build, with a G4600T and a dual slot GTX 1050 Ti.
Both CPU and GPU passively cooled.
The whole build is powered by a single 12V AC adapter.
By using a singe-slot GTX 1050 Ti, I figured you could go down to around 3L, that is with an external adapter.
You could certainly lower the volume by using a short GPU such as the GT 1030.