Many thanks for the welcome!
I have copied the entire Cfg folder from stock SH3 into GWX and played the training convoy mission - no crashes, killed the destroyer after sailing into middle of the convoy from behind him at medium speed/periscope depth, then toyed with the trawler. The trawler seemed rather clueless as to waht to do (do they only have hydrophones?) and was doing circles about 2 km behind the convoy as i lit up tanker after tanker after tanker (with torpedoes, not deck gun).
I guess i will need to try the same training mission in stock SH3, repeat all my steps and make sure that AI reaction would be identical... Or could anyone of the Grey Wolves confirm that if I replace the Cfg folder in GWX with that from stock SH3, the AI, sensors and the overall gameplay would be SH3's? I'm a noob and it is hard for me to second guess whether AI is broken
EDIT: Just played the same mission in stock SH3 and had exactly the same behaviour from the AI. So... it looks like, if one likes the GWX graphics but thinks that it is too hard (not just too hard, too little sneaking fun - AI seem to see you too soon too easily. To me the whole beauty of U-boats is in their sneakiness

), copy and replace Cfg folder from stock SH3 into the GWX. I'll update if I run into some trouble.