Bang-for-buck upgrades

[PJO]

Good pick up by @HamboCairns. The 2018 X calibre came out with the boost QR141mm hub spacing. Likely the fork also QR.
OP wants to upgrade fork and frame so will require new wheels...

 

[HamboCairns]

Doesn't really change much, the length/diameter proportion of the fork will have much more effect on stiffness & performance than the axle type.

I'm sure it will compared to the existing fork but why would you spend big now only to have to put a 9mm QR axle on a more trail focused setup?

 

[HamboCairns]

Good pick up by @HamboCairns. The 2018 X calibre came out with the boost QR141mm hub spacing. Likely the fork also QR.
OP wants to upgrade fork and frame so will require new wheels...

And with most new frames being 148mm rear axle, it would mean more faffing with the rear axle.

Just save for a new frame and wheels or even better a whole new bike. Sell yours when you've saved enough.