I’m currently searching.
Trying to decide between a 1×10 with narrow wide and secret granny (a granny you shift to by hand for long ups) and a 2×10.
It’s a pity that CRC have stopped doing their 1×10 bundles. It seems others (Wiggle etc) are out of stock too.
From my reading and research:
XT and up for the cassette so you can remove a ring when / if adding a T Rex.
Zee and Saint mechs aren’t brilliant for a 40t ring at the back. Some say they work, some have problems. SLX, XT, XTR for the rear mech. I went for XT.
A chain – pay your money and make your choice. They all seem much of a muchness. Cassette and chain bundles can save you a few pounds.
I like the look of Saint shifters but money’s tight. Zee get mixed reviews. I’m keeping an eye out on the classifieds but if I buy new, SLX or XT.
If I go 1×10, I think a Raceface narrow wide. They seem to keep their anodising better than others.