So I flashed this rom last night. Works great and still rooted. IMHO since your coming from different Android versions I would not flash a mod in the middle of flashing a new rom.
1. It may not be compatible with 4.4.2 framework etc.
2. Much like you I've been around this for awhile and it seems like with this phone there is no really easy way to get back to a previous version of Android without wiping everything. Upon flashing this rom the Kit Kat version overwrites the TWRP or custom recovery.
Personally I would wait to flash mods until someone cracks this and makes it where TWRP can work with Kit Kat. Which will not take too long I imagine. Xposed doesn't work yet with 4.4.2 missing that... Hope this helps!
Sent from my LG-D801 using xda app-developers app