30" radius from a #6 switch

How do you have a 30" radius when the radius of the switch does not look like 30"?

You wont, the #6 means the turn out track deveates 1 to 6 ratio of mainline travel and turnout is usually not curved. You can start your 30 " curve from the end of the turn out

A # 6 turnout is quite generous in terms of its ‘substitution’ radius. It works out to about 42" radius*, quite a bit wider than your 30" radius. So, if you were to overlap a 42" radius curved item that could just cover the width of the rails’ separation so that one part of the curve touched the end of the diverging route after the frog, and the other end of the turnout. at the points end, was also covered by the same arc, you would see that a 42" radius curve just sort of matches a #6…but not curved. The closure rails probably curve nearer to 28-30" radius, but then the frog and beyond are straight. So, you would have to rejoin, in a way, your rate of curvature just beyond the frog and hope to achieve what you are aiming for in your track plan.

I think you might find a #5 is a better match, but you would have to experiment.

*If the turnout complies with the NMRA specs for HO #6 turnouts.