Renaming outside of DPL is quite okay, but search will deliver false positives when the folders are renamed with DPL closed. If one doesn’t use search and projects, renaming is relatively straightforward indeed.
…in this case, you need to add an extra renaming step for these files. Nevertheless, it’s best to avoid duplicate names.
From what I understand it’s dangerous to rename while PL is running. As I understand, if PL detects a missing raw file, it will delete an associated sidecar. This can result in the complete loss of edits.
So just to be clear. Rename from within DXO or if you are renaming from outside Photolab then make sure Photolab is closed.
Depending on circumstances and goals, renaming gets more or less complicated. It’s best to not rename files and folders if ever possible.
Don’t save recipes and develop mostly from scratch - and renaming gets really simple.
Keep everything and edit on more than one computer - and you’ll have a hard time.
There is no free lunch. 
The main difficulty (horror, actually) with DPL in this area is, that it has no means to reconcile its database with what’s on the drive. This lack of feature makes DPL practically useless for asset management.
It’s scarcely believable that this wasn’t taken into account right from the creation of the tools in question …
No photographer works on his laptop when he’s on the move and on his workstation at his desk, is it ? (just an example here).
Many posts here deal with such or similar situations.
Here, it’s about bulk renaming and my tests showed that bulk renaming can be done, all while keeping DPL’s database in relatively good shape…as long as we don’t rename folders or move images to different folders.