In my world I get sever lag and fps drops a lot when the Miner is running.
If I move far away from the Miner or push tge "stop" button in the Miner the fps returns to normal and the lag is gone.

Ok, it worse than that.
I'v tried the same new world with and without NeoTech installed and as soon as it is installed the fps drops and the chunk generation/chunk loading gets very laggy.
I haven't even cretaed any items, just installed it.
Suggestion: check comminukation between client and server.

Same problem as #6?

After reading the code I wonder if there shouldn't be some "clientonly" and "serveronly" annotations or is that handled another way?

Should be fixed in rewrite. Initial release later today. Miner won't be in initial release