when you say tech, do you mean tech or more interesting than fireroads?
there are a few (europäische fernwanderwege) cutting through Bavarian, Austrian and Italian alps. as far as i know there aren’t any rules preventing you from riding them.
there is the Maximilainsweg (path number E4) which runs through Bavaria. starting in Lindau on the shores of mainland suropes largest lake (Bodensee) in the south-west ending in Berchtesgaden on the shores of Bavaria’s prettiest alpine lake in the south-east.
it takes in pretty much all of Bavaria’s alpine highlights including the “disney castle”, various picturesque lakes and breweries (Meckatzer, Tegernseer!!!). it’s about 350km long so should keep you happy for a week or so.
i’ve ridden sections of it and it is a well marked path with a few variations meaning you can ride your bike up on a fireroad rather than carrying it up a steep trail. not all sections are ideal for riding, but looking at your GR pics you are obviously not averse to a bit of adventure.
it’s something i’ve been wanting to do for a year or now now but haven’t had the time to kick it into action.
expect lots of short (1000hm) sharp climbs with lots of techy descending.
HTH