I just found a Reba for a bargain price and everything fits my frame except for the fact it uses quick release rather than axle; the rear dropouts are axle and with this fork the front will be QR, while I am up to changing my wheels because that was part of the plan, I wonder if it's a reasonable idea to mix QR and Axle, or if I should wait to find another bargain (who knows when) on a XC fork that has axle.
There's no fundamental reason why not but it would be an unusual combination. Through-axle fork with QR rear is much more common.
Bear in mind though that there are good reasons why through-axle designs have replaced QRs over the last 5-10 years. It helps make the fork stiffer and it prevents any chance of the front wheel being ejected from the dropouts under disk braking forces. You might also find it harder to find a suitable quality front wheel these days if you're restricted to QR compatible hubs.
(The term you want is "thru-axle.")
It's a little backwards-looking but there's no critical reason not to. How wise it is depends a lot on what kind of rider you are; riders towards the smoother and/or lighter end of the spectrum are going to get less benefit from a thru-axle front. There are a handful of bikes that come this way because they're at the lower end of a model line where the frame is the same throughout.
While product recommendations are off-topic here, QR Rebas are good forks that a lot of people ride very happily, and thru-axles being common now doesn't change that.
One consideration if you're looking to get fancy wheels now with 15mm thru-axle adapters available and run them QR for the time being is that if you do wind up upgrading the fork again, unless we're talking about a 26" bike then you may very possibly want to get a Boost 110 fork, and while many normal 15mm thru hubs can be adapted to Boost 110, they fundamentally can't take advantage of its upside because the whole point is to get the flanges further apart than normal 15x100 hubs allow.