Just trying to buy forks & need to know if Deore hubs can all be converted from standard QR to 15mm. Is there a big performance improvement from standard to 15mm? Any advice appreciated.

I dont think you can convert any shimano hubs can you, definitely not Deore anyhow.

15mm stiffens things up somewhat, just a pain with having to buy new wheels. If you are getting new forks id say it is worth doing, but really depends on your riding TBH, if you are just pootling then stick with 9mm qr, if you are thrashing the peaks then 15mm will flex less and track better etc etc

Thanks for that. Trying to build a fairly cheap bike so I’ll probably stick with 9mm.

No. But I’m sure they did a 20mm XT hub a few years ago.
If it helps, I rebuilt a front wheel that had an XT (760 I think it was) hub, with a Hope Pro2. Both have different spoke hole PCD’s & offsets, but just happen to use the same spoke length.
Building a wheel is straightforward enough.

Fit a solid axle with nuts in the meantime..