Beware of the infamous P class on Lufthansa. It credits 0% to TK (and other *A ffps). You can also forget about gettings miles and status credit from the likes of Eurowings.

TK Elite (*G) is certainly better than M&M Silver, but it will be a drop down in what you are used to with M&M Gold. It will be hard to recommend M&S when the plan is to continue flying almost exclusively on LH Group airlines. If you switched some of your business to TK it would be different.