Hey everyone! This forum has been absolutely fantastic brimming with ideas for modding this PC-TU100 case.
I took a pretty quick and dirty approach into modding my case. I ended up sawing a hole to the bottom of the case for a single 120mm fan as well as change the case feet for something less scratchy and higher to improve airflow from the bottom fan to the GPU.
I came across an engineering sample i7-8700T on ebay which was the perfect choice for this limited space case since the CPU is only 35 watts and therefore pretty easy to keep cool. I had a spare horizontal CPU cooler (Absolutely no idea about the brand, probably something cheap from China which outlasted the LGA1155 motherboard it came with).
I also got my hands on a second hand MSI Z370i motherboard for cheap (had a broken SATA port, which was no problem for me whatsoever since I only need one for Bluray drive and 1tb M.2 is enough for my needs).
Full specs of the computer:
CPU: i7-8700T (ES) 35w 6c/12t
Motherboard: MSI z370I Gaming Pro Carbon AC
RAM: 16 gigs of 2400mhz DDR4
GPU: Asus GTX 1660 Phoenix OC
PSU: Silverstone SFX 650w
Temps are quite good, too. Ran about an hour of stress testing with 3D Mark and IntelBurnTest. GPU temps didn't increase past 79C degrees and CPU was only at 57C at worst.
Some build pictures here. Pardon the blood stains on the feet, some aluminum shred cut my thumb