Hi there,
No real harsh impact, Better to build with SYSbuild anyway, less to deal with Especially if you plan on using the BLE OTA. and it’s only in the Preview, 2.8.0 and 2.9.0 you can build what you want.
things like the MCU Boot being a child of the APP now it’s all the same. no a big deal. You used to have to build them separately , then together now , all prebuilt ,pre-linked-and added in the bootloader then all partitioned in place. Allows way more options on DFU. 
HTH
GL 
PJ 
DO those DEV academy lessons to get a good handle on it, Also if you’re Switching to a better BOOTLOADER (MCUBoot) this is the ONLY way to GO! IMO. YMMV
The key is the BootLoader (so many options)
Yes a double press of the Reset button Still works… to trigger BL Mode! 