Does Upgrade with Avios use same availability as full redemptions

[squishsquash]

If I was to upgrade a cash Qatar Airways ticket with Avios (which ranges between 45 and 85k depending on economy fare class for the Man-Bkk route we take often)
Would there have to be ‘standard avios’ availability on that flight.

Ie if i can’t do a full redemption anyway does this mean it won’t be available?
Some flight have the flexi for double avios you see.

Wondering if anyone knows he ins and outs of this?

Thanx in advance