Hi Stephan,
I caught the two planetaries you mention in 2014 with my 12" Newtonian (2014 was a good year for me, observing-wise).
NGC 6765 - I found that it was not easily visible without the OIII filter in place. The OIII filter reveals a fairly large but dim disc. x375 shows an elongation, but the best view was obtained with the Or6mm eyepiece (x250) with the OIII filter. With this the elongation was clear and there were two tiny twinkles involved in the main section of the nebula. A fainter, detached section could be seen paralleling the main section.
M 1-64 (I have it listed as PNG 064.9+15.5) - Very small and very faint. Almost stellar. Not visible without the OIII filter, and quite hard to detect even with it. Elongation was suspected. In the 4mm eyepiece (x375) without the OIII filter the object was barely visible, and appeared like a fuzzy star. After much viewing at x150, it became just visible without the filter.
I haven't seen either of the two galaxies you mention - too faint for my poor skies, but I have seen other galaxies in Lyra, namely NGCs 6646, 6675, 6702, 6710, 6745 and 6792.