Hi Daniel,
If the system is booting and you can access all of your devices there is no need to change anything. If you want to make sure PCIE slot bandwidth is optimised you can go into the BIOS and check the settings. Refer to the user manual for details.
In 4 way SLI, according to page 24 of the user manual, you should be able to run x16, x8, x16, x8. If you have any U.2 devices connected and run the last slot in x8 mode the U.2 devices will be disabled. To enable the devices you need to change the bandwidth of this slot to x4.
Refer to pages 79-80 for more details of changing PCIE slot bandwidth.
Hope that helps.