You could try something like this.
I have an UpHere aluminum brace I bought from Amazon and it works great.
I mean it can't hurt. I just bought this and luckily it worked.
https://www.amazon.com/dp/B076GYL25H?ref=ppx\_yo2ov\_dt\_b\_product\_details&th=1
I'd seriously be looking in to upgrading the case to something with better radiator support. I'd personally get an O11 dynamic and upgrade to a 360mm AIO, or the O11 mini if you really want to keep your 240mm (280mm works better with the mini though).
You could put your AIO up front and mount your GPU AIO up top. You definitely don't want it on the bottom, you need your radiator above your pump to prevent damage to the pump. It's a bit more complicated, but that's the simple version. Tubes should travel down to the pump, not up.
Your modular power supply should be just fine for this with the included cables.
I'd probably use a fan splitter/hub and wire manage it in the back if possible.
I like the UP here! better and use it personally. https://www.amazon.com/upHere-Graphics-Anodized-Aerospace-Aluminum/dp/B076GYL25H/ref=sr_1_1?crid=EIHNM5MVOTL4&dchild=1&keywords=uphere+brace&qid=1613548834&sprefix=up+here+%2Caps%2C161&sr=8-1
3dmark. That's what I use, it's what a lot of people use. Includes firestrike and timespy. It's technically free, but it's well worth the money to pay for it just to skip demos. Cut's the run time in half, or at least it feels like it. Money well spent to me.
100mhz core 300mhz V ram at stock voltages should be more than doable even for a noob with X1 or afterburner, never mind on a high end hybrid card. Literally type in +100 and +300 on your respective fields and let her rip.
I had THIS gpu support bracket not being used. I zip-tied a 120mm fan to it to help cool my card and the chipset. It's worked well so far.