Gentleman, can somebody spoonfeed me?
Building around a Lian Li x Dan Cases A3

Can I please have some help choosing

7800X3D vs 9800X3D, is it worth the extra money?
Which AIO do I choose
Which PSU will fit
What memory to choose price/performance
How do I mount my two 3.5" HDD's, do I need to buy an external DAS/HDD enclosure
I am keeping my 3080 for at least a few more years.