Yes. It flashed with OxygenOS but OTA function is disable, you will see no network connection when enter the update section.

Banking apps are not affected even if you're rooted as long as you get the KernelSU Next & its components updated & running well. So far banking apps I tried (HLB, PBB, MBB, UOB & CIMB), even e-Wallets app (TNG, Grab & Boost).

You can always use unlock the bootloader again, flash back to ColorOS & lock the bootloader if you want hassle free. I found no advantages using OyxgenOS beside bunch of bloatwares needed to be remove in ColorOS. Performance wise, it's almost identical plus faster OTA.

did you lock it back after flashing?

it will since bank app wont work if it is rooted or unlock ... worst now if you are on dev mode or got shizuku  all cant work

i cant seems to find what is wrong with your phone though 

Shouldn't have flashed to oos since cos is pretty nice to use these days.

OOS 15.0.0.305(EX01) version is the version that preloaded by CN version, I didn't use this because I already restored all back to COS latest version, has no issue with the MAE & CIMB app with lock bootloader.

I think u should update to latest OOS before you setup u phone, now if u do u have to wipe data & redo all again, or just settled down with the slow app issues but do u think it's MAE or CIMB app issue or OOS itself if other apps running fine?