I’ve got a small amount of sag with my 3080 Ti, both with the stock air cooler and with the water block I installed. It definitely isn’t half an inch horrible though, and the card suffers no ill effect aside from maybe triggering someone’s OCD.

EK Block on my 3080FTW3 .....dont notice any sag...although I did throw a zap strap around one of fittings to a PCI-E plug to provide a little more support.....and really even the tubing provides support as well.

cmeyer3151
All 3 of mine are water blocked and I use these:
 
 
https://lian-li.com/product/gb-001/

I use these as well for builds where the mobo case mounting screws are not blocked by a heat shield.  These are great and very inexpensive option to help support the gpu while keeping a clean look.  

My 3090 sagged enough that I went out to the shop and cut a small section of 1x2 lumber to put under the far corner for support.

It won't be in that machine for long, it's destined for the new build I'm working on, which will have the card vertical.

Couldn't see not using it over my aging 950's until the new machine is finished. :)

I don't use a sag bracket on my 3080 Ti FTW3 Ultra. I have the PCIe cords running from the top, across the back plate into the case so this holds the card up to me pretty well. 

there was definitely a pinch of sag with my 3080 ti FTW3 Ultra when I had the air cooler on it. It was the the most chonky GPU I've ever seen. I swapped in the hybrid cooler and when hold it straight before tightening the I/O bracket screws nice and snug, there's no detectable sag. I have an EVGA motherboard though, which is stiffer/thicker than most, and my case is fairly robust and solid as well, so I think if you have both of those, your sag is minimized. That said, with the stock air cooler, I probably would have worried just enough to buy an anti-sag bracket of some kind.

Do these fit most cases?

Not using a bracket with my 3090. 

I do not, but my MB lies horizontal in my cases, so no need for bracket. 

I bought a bracket for a 3080 FTW3 Ultra. But when I started installing it I just stopped and returned it. The sag was so minimal and there is no way its going to break anything if I didn't install it. And this is a Thicc card. I think it weights almost 4 lbs.

dlbsyst
I'm not experiencing any sag with my 3080 ti FTW3 Ultra. Because of how wide the card is it barely fits inside my O11 Dynamic. My 3 Pci-e cables actually touch the glass and it holds my card nicely.🙂

Same sentiments. Though i'm not sure if having reinforced steel brackets on the mobo pcie slots itself helps as advertised.

On the RTX 3090 FTW I had previously, I did not use any extra support bracket. I did not notice any sag. 

I don't use the one that comes with the card, as my computer case already has one cooler master h500m, I use that one. 

Just like anything in life there is no general rule that always applies all the time. There are unique builds with varying amounts of sag and the builders have requirements for what is acceptable, experience does not apply here. (not only talking about sag here but pretty much everything about computer builds due to all the variables at play)
 
Look at the backplate of your card and use the PCI-E slot (and other parallel lines for reference) and see if there is a considerable amount of sag and decide if it matters to you. Regardless of long term effects/aesthetics I think the general consensus is less/no sag is better than having sag. Some people pursue making things as right as possible and I can respect that.
 
"Yeah? Well, you know, that's just like uh, your opinion, man." -The Big Lebowski

Vertical mount with phanteks bracket in lian li 011d
no sag