Serafil is a better quality thread. I managed to get my consew 206rb1 to sew QTC 270. Had to use #69 thread in the bobbins and mess with the top tension quite a bit
I use tac glue on most projects unless its leather. I spray a light coat and it dissolves over time so it doesnt cause any creases in the material after regular use.
We have recently started using Alea leather kits in the past 5-6 months with great results. Fit and finish is nice and they turn out well with a little finessing