and then my screen went black and came back on and my resolution was really big and all my colour settings had changed and it said my AMD display drivers has crashed. I restarted my pc to see if it would fix anything and then the screens haven't turned on since
This indicates GPU failure.
After I put in the different PSU the PC booted twice normally.
But you were using your RX 5700 XT still? If so, PC can not boot normally when you have a dead GPU and you don't see an image.
Original PSU: Gigabyte P650B
Low quality PSU.
PSU came with mere 3 years of warranty and when you bought your PC in 2021, that makes PSU now 4 years old. Which, given it's warranty length, is actually quite good. Given that the Gigabyte unit still somehow works and wasn't a reason behind why your GPU died on you.
Still, since your PSU is low quality, past it's expected operation date and you had GPU die in the build, i suspect PSU was the one that killed your GPU.
It's a Raidmax Vampire 700w from what I know.
That PSU has even worse build quality than your Gigabyte unit. Another low quality unit, borderline crap quality.
so could anyone point me in the right direction?
1. New, good quality PSU.
2. New (or borrowed) known to work GPU.
New PSU is needed so, that your old low quality PSUs, won't kill new (or borrowed) GPU.
New (or borrowed), known to work, GPU is needed to validate if your GPU is toast.
When image shows up and build works fine otherwise, then it was easy solution. Your old GPU is dead (most likely killed by the poor PSU you have). And fix is new GPU and PSU.
But if the image doesn't show up even with 2nd, known to work GPU, then one of the following (or all of them) are dead: CPU, MoBo, RAM.
So, 1st, new, good quality PSU is needed.
If you plan to keep RX 5700 XT (IF it survived) or equally same TDP GPU (225W), then 650W PSU is minimum. Though, i'd be comfortable with 750W unit.
Good PSUs to go for, are: Seasonic Focus/Vertex/PRIME, Corsair RMx/RMi/HXi/AXi, Super Flower Leadex Gold/Platinum/Titanium.
Or if you want the latest ATX 3.0/3.1 PSU, then:
https://hwbusters.com/best_picks/best-atxv3-pcie5-ready-psus-picks-hardware-busters/3/
(My 3x PCs are also powered by Seasonic. I have 2x PRIME TX-650 units and one Focus PX-550 unit. Full specs with pics in my sig.)
Once you have 2nd, good quality PSU, look towards 2nd, known to work GPU (either buy one or borrow). Then, when PC is powered by new, good quality PSU, put the 2nd, known to work GPU into the build and look if you can see an image.