Audio production build + question about lane sharing

Hi all,

I'm trying to build an m-atx pc for audio production. That's why this build prominently lacks a dedicated graphics card. See the build in the table below.

I feel pretty confident about it, but I do have an important question regarding the motherboard (ASRock B850M Steel Legend WiFi). I need to know if the m.2 slots share lanes with any of the pcie slots, especially the bottom pcie x4 slot, since I want to use that one for a firewire pcie card while at the same time using all 3 m.2 slots.

I can not for the life of me find any explicit statements mentioning any lane sharing behavior. Please, if you can help me figure this one out, I'd be very grateful. Of course, feel free to comment on the other components as well.

Bonus question for pc+audio nerds: Does it matter in which m.2 slots i put the three ssd's, considering their specific functions?

Thanks a lot!

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CPU: AMD Ryzen 5 7600X Processor

MOBO: ASRock B850M Steel Legend WiFi

CPU COOLER: Scythe Fuma 3

RAM: Patriot Memory Viper Venom 2x32GB 6000Mzh CL30 PVV564G600C30K

SSD 1 (OS + PROG): WD Black SN7100 500GB M.2 SSD

SSD 2 (PROJECTS): Lexar NM790 2TB M.2 SSD

SSD 3 (LIBRARIES): Lexar NM790 2TB M.2 SSD

BACKUP HDD: Western Digital My Passport external hdd 5 TB

CASE: Lian Li A3-mATX Black

CASE FANS: 3x Arctic P12 PWM (2x intake, 1x exhaust)

PSU: be quiet! Pure Power 13 M 550W PSU