Would hurt you wallet if you don't really need it and if you go RTX 40xx ,you'll need another PSU and probably a bigger case
Not sure if i understand this very well ,but for HDD /SSD ,ports are SATA data on the motherboard (you have 6 of them in theory ,5+1 used by your actual SSD) and SATA power from the PSU. Can go nvme2 M.2. for the SSD too
PCIE on the MB ,you should have 2-3 of them+2 (6+2) pins cables ,you should have 2