Your specs are good enough to run SH5 well
restrict your TC to x 64 when near Kiel and you should be ok

The flag issue will go away soon and will stay away untill you change your mod list and then it will come back. This only ever lasts a save/load or two.
OHII uses radio messages from the stock radio (captains log) and from TDWs radio message box - so yes you will get messages from both.
Some will be of high importance and you will be told
Sink em all