gpu length and width, case width and length, cpu cooler height. Also with the top of case be removable? (for reservoir orientation and stuff)
gpu length and widths are tricky.
Internally, the space between the front panel and back panel is 305mm, but the space between flanges is 285mm. So GPU smaller or equal to 285mm long fits, between 285 and 300 it may be possible but you will really have to "jimmy it in there" creatively. I maintain the opinion that it can be done but with difficulty. I would like to obtain a REALLY big gpu to try it to asses if i should trim the flanges back or if there is no point. Width from GPU pcb to inside of flange is 50.3 mm (2.5 slot). There is a small gap between the side panel and flange that could afford you an extra 3mm but i figured its best left as an air gap between fans and panel to prevent noise from turbulence. So something like an Asus strix 2080 ti is not going to fit, but an MSI 2080ti Ventus or an EVGA 2080ti XC or a Gigabyte 2080 super gaming OC should fit, (i did not test any of these, just judging by their product dimensions).
Case width and length with side panels is roughly 135mm by 315mm. Roughly because of manufacturing tolerances. I can wish it all I want but no fabricator would be able to hit those dimensions exactly (and be affordable). I reckon +/- 0.5mm at best.
Top of case is not removable. For reservoir fitment here are some things to consider: Internal width is 126mm (give or take). Assuming a 30mm radiator width with 25mm fans that leaves you with 71mm of space, (more if you dont mount behind the flange). This is enough to fit a DDC pump with a reservoir top in front of the fan, above the GPU. The EK offerings (especailly with the smallest reservoirs) would likely work. I Imagine you could definitely fit a Phanteks Glacier R160 in there with a DDC pump somwhere. Either in lieu of the 60mm fans in the back or affixed to the top horizontally (although you would have to get creative with how you attach it). The clearance between MB and internal flange where the 60mm fans are is actually 70mm so you could conceivably mount a DDC there as well instead of a 60mm fan. The 60mm fans have 50 x 50 mm hole spacing, the EK DDC has 49 x 49mm. the holes are big enough, it will fit. My personal favorite, and what I plan to do with mine, is an Aquacomputer Ultitop for a D5 pump with an alphaccol Cape Corp Coolplex Metal reservoir mounted on a pair of rotary 90 degree adapters. That way i can lay the case on its side and "rotate" the reservoir upright for filling and bleeding, then seal it up and tuck it back into the case. Heres a close up render of that (the very white blob is an LED plug, maybe a tad too bright in the render):
I prefer to mount 1 or 2 90mm fans opposite to the motherboard, rather than 2 mini fans on the back. Mini fans usually are louder and less efficient than larger fans.
Could you clarify what you mean by "opposite to the motherboard"? Like above it? facing the vented side panel?