If you have the Bren pistol that came with the low profile sights similar to the ones on the Scorpion, then the OEM stocks both the collapsible and non-collapsible (both folding) without the cheek risers, work. I am assuming that cheek weld is also good with the Zhukov stock w/adapter and AR stocks used with the adapter from KNS.
If you have the folding sights that come with the carbine, then you will need a cheek riser. This is especially true if you use a red dot sight or a scope with a standard AR height mount to achieve a co-witness. I have seen "operators" use the OEM stock without a cheek riser because it gets in the way of either their helmet, comms or both. I ended up using an OEM collapsible, folding stock but replaced the cheek riser with one from Magpul designed for their AK stocks. It just feels more comfortable than the slanted clip-on riser they had. Again, each will have their preference as to what works, what looks good, etc.