I'm looking for a new rear wheel or hub to go on my 2014 Specialized demo 8, cant find many, needs to be 12mm X 148-150mm, i can find some, but not many that are 10 speed, all 11 speed, any help or knowledge much appreciated!
From that era it's probably 150. Measure the frame to check. If so you cannot use 148/boost. There may be some boost hubs and wheels around now that have endcaps for 150. If so it's not common and would require re-dishing if it's a wheel. (If memory serves, the very first boost bikes were in the 2015/2016 timeframe, and 2017 was the year it became big).
In case it's not clear, yes the 2mm matters critically on any full suspension and/or thru-axle bike. Compressing the rear end is going to play havoc with the hub and pivot bearings, and will put extra stress on the dropouts and axle. There are bike applications where rear end spacing is malleable, but not on aluminum and not when there's a thru-axle involved.
For mountain HG hubs there is no 10/11 speed distinction. If you come across a 150x12 wheel that says it's 11-speed HG, your 10 speed cassette will work without issue.
The premium hub makers mostly all have a 150 product to offer. If you want more basic than that but not garbage, the simple answer is to get the Shimano Zee hub or something with a Novatec hub, which could have any number of brands on it. It's not a good application to go cheaper than that. DH bikes get a lot of benefit from just going to a money rear hub.