C4 looks like it won't support a good chunk of modern RTX 3000 series cards in classic layout. Dan has already confirmed in thread that he won't increase size to increase compatibility. I can't say for sure since there are no third party reviews yet, but it looks like it uses similar build quality from Lian Li with the thin panels. I trust Form D's panels / build quality much more based on what I saw with T1.
C4 has a number of features that should help with compatibility, like a hole at the front that extends max GPU length compatibility further than the frame. In addition, the 4.0 Riser Card planned for the C4-SFX doesn't sound like it will have the issues of current 4.0 Riser Cables, so Sandwich Layout should greatly increase compatibility with large Ampere cards without hurting performance or anything - especially now that it can be flipped and support a 280mm rad and two slim fans while doing this.
That said, having owned neither the T1 or M1, I can't address any worries regarding build quality.
I thought we were trying to create a bigger case than T1 here? Or are we trying to get the same size again? Because T1 is a sandwich, AIO-friendly case 9.5L case, why would you want to do a second model of a new case that is also going to be exact same sandwich / AIO-emphasis 9.5 L case then?
100% agreed. The T1 is a fine case that meets its goals well - so borrowing some improvements from the originally planned P1 for a V1.2 of the case, such as additional spine positions would be good, while keeping it below 9.5L.
That said, personally, I would have preferred having a proper, separate case that has its own size & features, such as 280mm support, classic layout support, vertical layout support, larger size, etc. That said, it'd probably cost more in machining, logistics, etc.
Either way, regardless of how it's done, I think we're all still very much in the dark about what this case (The T1 EVO) is supposed to look like and support. We've heard things tossed around like classic layout support, multiple 240mm rads, changing case size, not changing case size, vertical support, etc etc etc.
But we still don't have renders or even a list of planned changes on the first post of this thread.
It's all just been tidbits of 'I'm planning this change, also may do this, also might change this - would need to do this if we did this" etc etc etc.
I just hope people temper their expectations and wait for details to be confirmed & shown before getting hyped.
(Please note, I'm not saying the case won't be amazing, but rather just that we don't know what is 100% happening yet. Just speaking as someone who got burned by the eWhite T1 and QC issues - things happen, even right up to shipping.)