I’ve always used a 20p for C#. Never had an issue. Can’t stand a wound G. Usually for C# would do a 12-52/53 with the plain G. Don’t care for >53 on the low E (Gibson scale) as you lose attack and bite on palm mutes and false harmonics etc. plus 12-53 sets up perfectly, with no neck adjustment required, when I change from 10’s at A440. Intonation just needs a little tweak.
I know you’re having a luthier involved but are they really getting the nut and bridge slots right for the gauge, which could be giving you such a glaring difference?