5700xt is something like 6% slower than rtx 2070 super on multigame avg fps. benchmarks. So a lot faster than 1660ti (close to +50%).
I would maybe downgrade psu a bit and go for tx550m instead and buy a tower cooler for cpu.
https://www.globaldata.pt/catalog/product/view/id/10430/s/cooler-cpu-arctic-freezer-34-acfre00052a/
https://www.globaldata.pt/fonte-bitfenix-formula-550w-80-gold-bp-fm550ulag-9r or https://www.globaldata.pt/fonte-semi-modular-corsair-tx-550m-80-gold-cp-9020133-eu
Also ssd swapped to sata model saves 20€ too. There is pretty much no difference in games.
https://www.globaldata.pt/componentes/discos/ssd/disco-ssd-blueray-ultra-m8s-480gb-3d-tlc-sata-iii-sdm8si480a
Nova Mesh looks like a nice case.
https://www.globaldata.pt/caixa-atx-bitfenix-nova-mesh-preta-bfc-nvm-300-kkxsk
And get one or two fans for intake. https://www.globaldata.pt/ventoinha-arctic-cooling-p14-pwm-pst-preto-acfan00125a
I would take that front top roof fan out completely. No use to blow air out before it heat ups from any components and if intake it will only create turbulance for the front panel intake.
http://www.skytech.lt/cp9020133eu-psu-corsair-tx550m-550w-plus-gold-semimodular-120mm-p-343851.html
http://www.skytech.lt/cp9020177eu-psu-corsair-rmx-series-rm550x-550w-plus-gold-fully-modular-140mm-p-386048.html
RMX is better and has 10 year warranty.
Just make sure nothing is hitting the fan blades. That should be relatively quiet even at max rpm. And you can always lower the rpm, buying a Noctua fan will make about 0 difference if you run it with similar rpm:s.
Just put that radiator in front panel as an intake and you wont heat up your cpu with gpu.
That depends a lot on what cpu you run. If I remember correctly Tweaktown tests with a 4770K with low voltage(1.15V or something like that) so you cant see differences with high-end and middle class coolers.
What version of Prime are you running? And you can always play with the power limit setting too. So that you set the length so that clocks stay high while gaming, and drop an all core avx load.
You could always pick an MSI board with biosflashback function if no MSI b450 max boards are for sale. Those MSI max-versions are new with a larger bios chip and will support 3000-series out of the box.
https://www.reddit.com/r/Amd/comments/bvfo57/list_of_b350_b450_x370_and_x470_motherboards_with/