Just had a look at the On One AL30s and the free-hub Shimano/SRAM flavours are either 11 speed or 10/11 speed.

I’m running 9 speed Shimano at present – I’m guessing the 10 Speed freehub is one to go for?

If you go 11 speed wheels, they may have an 11 to 10 speed spacer like my RS81 shimano wheels did. Check with on one. You can then use 10 to 8 speed cassettes on the wheels. If you buy 11 speed, you can upgrade to 11 in the future, without issues.

Your 9 speed cassette will just go on a 10 speed freehub With a 10 /11 speed you’ll need a spacer. The AL30 Wheels are not very good BTW the freehubs are rubbish and break easily and the bearing last months not years.